Method and device for supporting repetitive CSI-RS resource transmission in mobile communication system

ABSTRACT

The disclosure relates to a communication technique for convergence of a 5G communication system for supporting a higher data transmission rate beyond a 4G system with an IoT technology, and a system therefor. The t disclosure may be applied to an intelligent service (for example, smart home, smart building, smart city, smart car or connected car, health care, digital education, retail business, security- and safety-related service, etc.) on the basis of a 5G communication technology and an IoT-related technology. A method in a wireless communication system is provided. The method includes transmitting channel state information reference signal (CSI-RS) configuration information to a terminal, the CSI-RS configuration information used for a CSI-RS resource set which includes a plurality of CSI-RS resources and information on CSI-RS repetition, transmitting a plurality of CSI-RSs based on the CSI-RS configuration information to the terminal, and receiving feedback information from the terminal, wherein the information on CSI-RS repetition indicates whether the plurality of CSI-RSs are transmitted based on a same transmission beam repetitively.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based on and claims priority under 35 U.S.C. §119(a) to Korean Patent Application Ser. No. 10-2017-0111275, which wasfiled on Aug. 31, 2017, in the Korean Intellectual Property Office, theentire disclosure of which is incorporated herein by reference.

BACKGROUND 1) Field

The disclosure relates, generally, to a wireless communication system,and more particularly, to a method and device for transmitting, by abase station, a channel state information reference signal (CSI-RS) forchannel state measurement of a terminal.

2) Description of the Related Art

In order to meet wireless data traffic demands, which have increasedsince the commercialization of a 4G communication system, efforts todevelop an improved 5G communication system or a pre-5G communicationsystem have been made, which is sometimes referred to as abeyond-4G-network communication system or a post-long term evolution(LTE) system. In order to achieve a high data transmission rate,implementation of the 5G communication system in an mmWave band (e.g., a60 GHz band) is being considered. In the 5G communication system,technologies such as beamforming, massive multiple-input multiple-output(MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analogbeamforming, and large-scale antenna technologies have been consideredas a way to mitigate propagation path loss in the mmWave band andincrease a propagation transmission distance. Further, in the 5Gcommunication system, technologies such as an evolved small cell, anadvanced small cell, a cloud radio access network (RAN), an ultra-densenetwork, device-to-device communication (D2D), a wireless backhaul, amoving network, cooperative communication, coordinated multi-points(CoMP), and received interference cancellation have been used to improvethe system network. In addition, in the 5G system, advanced codingmodulation (ACM) schemes, such as hybrid frequency-shift keying (FSK)and quadrature amplitude modulation (QAM) (FQAM) and sliding windowsuperposition coding (SWSC), and advanced access technologies, such asfilter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA),and sparse code multiple access (SCMA), have also been developed.

The Internet has evolved to an Internet of things (IoT) network, inwhich distributed components, such as objects, exchange and processinformation from a human-oriented connection network in which humansgenerate and consume information. Internet of everything (IoE)technology, in which big-data-processing technology based on aconnection with a cloud server or the like is combined with IoTtechnology, has also emerged. In order to implement the IoT, technicalfactors such as a sensing technique, wired/wireless communication andnetwork infrastructure, service interface technology, and securitytechnology are required, and thus research is being conducted these dayson a sensor network, machine-to-machine (M2M) communication,machine-type communication (MTC), and the like for connection betweenobjects. In an IoT environment, through collection and analysis of datagenerated by connected objects, an intelligent internet technology (IT)service that creates new value in people's lives may be provided. TheIoT may be applied to fields, such as those of a smart home, a smartbuilding, a smart city, a smart car, a connected car, a smart grid,health care, a smart home appliance, or high-tech medical services,through the convergence or combination of the conventional informationtechnology (IT) and various industries.

Accordingly, various attempts to apply 5G communication to an IoTnetwork have been made. For example, 5G communication technologies suchas a sensor network, M2M communication, and MTC are implemented usingtechniques such as beamforming, MIMO, and array antennas. Theapplication of a cloud RAN as big-data-processing technology is anexample of convergence of the 5G technology and the IoT technology.

In new 5G communication, that is, the new radio (NR), communication isperformed based on beams, unlike the existing LTE; this is because NRsupports a band higher than 6 GHz, which is higher than the conventionalLTE band. Further, since there are not many conventionally used systemsin such a band, more band can be secured. However, in order to support aband higher than 6 GHz, in addition to those affecting the use of bandsin existing LTE, path loss due to the increase of the band also needs tobe considered. For example, as a band used for wireless communicationincreases, path loss occurring in the corresponding band also increases.Further, due to the pass loss, the coverage supported by a correspondingbase station decreases for the same transmission power. Therefore, inorder to overcome the pass loss, it is necessary to support a beam forconcentration and transmission of transmission power in the directionrequired by the base station, and since a direction that can besupported by one beam is reduced according to the support of thecorresponding beam, it is also necessary to efficiently select andmanage the beam.

SUMMARY

The disclosure has been made to address at least the disadvantagesdescribed above and to provide at least the advantages described below.Accordingly, the disclosure provides a method and device for efficientlyselecting and managing a beam.

In accordance with an aspect of the disclosure, there is provided amethod of a base station in a wireless communication system. The methodincludes transmitting channel state information reference signal(CSI-RS) configuration information to a terminal, the CSI-RSconfiguration information used for a CSI-RS resource set which includesa plurality of CSI-RS resources and information on CSI-RS repetition,transmitting a plurality of CSI-RSs based on the CSI-RS configurationinformation to the terminal, and receiving feedback information from theterminal, wherein the information on CSI-RS repetition indicates whetherthe plurality of CSI-RSs are transmitted based on a same transmissionbeam repetitively.

In accordance with an aspect of the disclosure, there is provided amethod of a terminal in a wireless communication system. The methodincludes receiving channel state information reference signal (CSI-RS)configuration information from a base station, the CSI-RS configurationinformation used for a CSI-RS resource set which includes plurality ofCSI-RS resources and information on CSI-RS repetition, receiving aplurality of CSI-RSs based on the CSI-RS configuration information fromthe base station, generating feedback information based on the receivedplurality of CSI-RSs, and transmitting the feedback information to thebase station, wherein the information on CSI-RS repetition indicateswhether the plurality of CSI-RSs are transmitted based on a sametransmission beam repetitively.

In accordance with an aspect of the disclosure, there is provided a basestation in a wireless communication system. The base station includes atransceiver and a controller operably coupled to the transceiver andconfigured to transmit channel state information reference signal(CSI-RS) configuration information to a terminal, the CSI-RSconfiguration information used for a CSI-RS resource set which includesa plurality of CSI-RS resources and information on CSI-RS repetition,transmit a plurality of CSI-RSs based on the CSI-RS configurationinformation to the terminal, and receive feedback information from theterminal, wherein the information on CSI-RS repetition indicates whetherthe plurality of CSI-RSs are transmitted based on a same transmissionbeam repetitively.

In accordance with an aspect of the disclosure, there is provided aterminal in a wireless communication system. The terminal includes atransceiver and a controller operably coupled to the transceiver andconfigured to receive channel state information reference signal(CSI-RS) configuration information from a base station, the CSI-RSconfiguration information used for a CSI-RS resource set which includesa plurality of CSI-RS resources and information on CSI-RS repetition,receive a plurality of CSI-RSs based on the CSI-RS configurationinformation from the base station, generate feedback information basedon the received plurality of CSI-RSs, and transmit the feedbackinformation to the base station, wherein the information on CSI-RSrepetition indicates whether the plurality of CSI-RSs are transmittedbased on a same transmission beam repetitively.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of certainembodiments of the disclosure will be more apparent from the followingdetailed description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a diagram of a radio resource setting, according to anembodiment;

FIG. 2 is a diagram of feedback timing of rank indicator (RI) andwideband channel quality indicator (wCQI) when N_(pd)=2, M_(RI)=2,N_(OFFSET, CQI)=1, and NOFFSET, RI=−1, according to an embodiment;

FIG. 3 is a diagram of feedback timing of RI, subband CQI (sCQI), andwCQI when N_(pd)=2, M_(RI)=2, J=3(10 MHz), K=1, N_(OFFSET, CQI),=1, andN_(OFFSET, RI)=−1, according to an embodiment;

FIG. 4 is a of feedback timing when precoding type indicator (PTI)=0 andN_(pd)=2, M_(RI)=2, J=3(10 MHz), K=1, H′=3, N_(OFFSET, CQI)=1, andN_(OFFSET,R1)=−1, according to an embodiment;

FIG. 5 is a diagram of feedback timing when PTI=1 and N_(pd)=2,M_(RI)=2, J=3(10 MHz), K=1, H′=3, N_(OFFSET,CQI)=1, andN_(OFFSET,RI)=−1, according to an embodiment;

FIG. 6 is a diagram of periodic channel state reporting supported byterminals for which CSI-RSs of 12 or more ports are configured inlong-term evolution (LTE) release 13 (Rel-13) and LTE release 14(Rel-14), according to an embodiment;

FIG. 7 is a diagram of a radio resource setting of data, such asenhanced mobile broadband (eMBB), ultra-reliable and low-latencycommunications (URLLC), and massive MTC (mMTC), in an NR system),according to an embodiment;

FIG. 8 is a diagram of a synchronization signal that is transmitted in a5G communication system, according to an embodiment;

FIG. 9 is a diagram of a physical broadcast channel (PBCH) that istransmitted in the 5G communication system, according to an embodiment;

FIG. 10 is a diagram of services that are multiplexed in respective timeand frequency resources in the NR system, according to an embodiment;

FIG. 11 is a diagram of a base station and a terminal that allow for aflexible configuration through a resource setting, a CSI reportingsetting, and a channel state measurement setting in the NR, and in whichchannel state reporting is performed based on the flexibleconfiguration, according to an embodiment;

FIG. 12 is a diagram of a method for triggering a link within a triggermeasurement setting according to an aperiodic channel state reporttrigger method 1, according to an embodiment;

FIG. 13 is a diagram of an indication sequence of bitmaps for theaperiodic channel state report trigger method 1, according to anembodiment;

FIG. 14 is a diagram of a method for triggering a CSI reporting settingwithin a trigger measurement setting according to an aperiodic channelstate report trigger method 2, according to an embodiment;

FIG. 15 is a diagram of an indication sequence of bitmaps for theaperiodic channel state report trigger method 2, according to anembodiment;

FIG. 16 is a diagram of an indirect indication of an aperiodic CSI-RS byusing an aperiodic channel state report indication field, according toan embodiment;

FIG. 17 is a diagram of a hybrid beamforming system supported in NR,according to an embodiment;

FIG. 18 is a diagram of a beam-sweeping operation of a terminal and abase station in time resources, according to an embodiment;

FIG. 19 is a flowchart of a method of the terminal, according to anembodiment;

FIG. 20 is a flowchart of a method of the base station, according to anembodiment;

FIG. 21 is a diagram of a terminal according to an embodiment;

FIG. 22 is a diagram of a base station according to an embodiment; and

FIG. 23 illustrates a beam group (B) pattern according to an embodiment.

DETAILED DESCRIPTION

Embodiments of the disclosure will be described herein below withreference to the accompanying drawings. However, the embodiments of thedisclosure are not limited to the specific embodiments and should beconstrued as including all modifications, changes, equivalent devicesand methods, and/or alternative embodiments of the present disclosure.In the description of the drawings, similar reference numerals are usedfor similar elements.

The terms “have,” “may have,” “include,” and “may include” as usedherein indicate the presence of corresponding features (for example,elements such as numerical values, functions, operations, or parts), anddo not preclude the presence of additional features.

The terms “A or B,” “at least one of A or/and B,” or “one or more of Aor/and B” as used herein include all possible combinations of itemsenumerated with them. For example, “A or B,” “at least one of A and B,”or “at least one of A or B” means (₁) including at least one A, (2)including at least one B, or (3) including both at least one A and atleast one B.

The terms such as “first” and “second” as used herein may usecorresponding components regardless of importance or an order and areused to distinguish a component from another without limiting thecomponents. These terms may be used for the purpose of distinguishingone element from another element. For example, a first user device and asecond user device may indicate different user devices regardless of theorder or importance. For example, a first element may be referred to asa second element without departing from the scope the disclosure, andsimilarly, a second element may be referred to as a first element.

It will be understood that, when an element (for example, a firstelement) is “(operatively or communicatively) coupled with/to” or“connected to” another element (for example, a second element), theelement may be directly coupled with/to another element, and there maybe an intervening element (for example, a third element) between theelement and another element. To the contrary, it will be understoodthat, when an element (for example, a first element) is “directlycoupled with/to” or “directly connected to” another element (forexample, a second element), there is no intervening element (forexample, a third element) between the element and another element.

The expression “configured to (or set to)” as used herein may be usedinterchangeably with “suitable for,” “having the capacity to,” “designedto,” “adapted to,” “made to,” or “capable of” according to a context.The term “configured to (set to)” does not necessarily mean“specifically designed to” in a hardware level. Instead, the expression“apparatus configured to . . . ” may mean that the apparatus is “capableof . . . ” along with other devices or parts in a certain context. Forexample, “a processor configured to (set to) perform A, B, and C” maymean a dedicated processor (e.g., an embedded processor) for performinga corresponding operation, or a generic-purpose processor (e.g., acentral processing unit (CPU) or an application processor (AP)) capableof performing a corresponding operation by executing one or moresoftware programs stored in a memory device.

The terms used in describing the various embodiments of the disclosureare for the purpose of describing particular embodiments and are notintended to limit the disclosure. As used herein, the singular forms areintended to include the plural forms as well, unless the context clearlyindicates otherwise. All of the terms used herein including technical orscientific terms have the same meanings as those generally understood byan ordinary skilled person in the related art unless they are definedotherwise. The terms defined in a generally used dictionary should beinterpreted as having the same or similar meanings as the contextualmeanings of the relevant technology and should not be interpreted ashaving ideal or exaggerated meanings unless they are clearly definedherein. According to circumstances, even the terms defined in thisdisclosure should not be interpreted as excluding the embodiments of thedisclosure.

The term “module” as used herein may, for example, mean a unit includingone of hardware, software, and firmware or a combination of two or moreof them. The “module” may be interchangeably used with, for example, theterm “unit”, “logic”, “logical block”, “component”, or “circuit”. The“module” may be a minimum unit of an integrated component element or apart thereof. The “module” may be a minimum unit for performing one ormore functions or a part thereof. The “module” may be mechanically orelectronically implemented. For example, the “module” according to thedisclosure may include at least one of an application-specificintegrated circuit (ASIC) chip, a field-programmable gate array (FPGA),and a programmable-logic device for performing operations which has beenknown or are to be developed hereinafter.

An electronic device according to the disclosure may include at leastone of, for example, a smart phone, a tablet personal computer (PC), amobile phone, a video phone, an electronic book reader (e-book reader),a desktop PC, a laptop PC, a netbook computer, a workstation, a server,a personal digital assistant (PDA), a portable multimedia player (PMP),a MPEG-1 audio layer-3 (MP3) player, a mobile medical device, a camera,and a wearable device. The wearable device may include at least one ofan accessory type (e.g., a watch, a ring, a bracelet, an anklet, anecklace, a glasses, a contact lens, or a head-mounted device (HMD)), afabric or clothing integrated type (e.g., an electronic clothing), abody-mounted type (e.g., a skin pad, or tattoo), and a bio-implantabletype (e.g., an implantable circuit).

The electronic device may be a home appliance. The home appliance mayinclude at least one of, for example, a television, a digital video disk(DVD) player, an audio, a refrigerator, an air conditioner, a vacuumcleaner, an oven, a microwave oven, a washing machine, an air cleaner, aset-top box, a home automation control panel, a security control panel,a TV box (e.g., Samsung HomeSync™, Apple TV™, or Google TV™), a gameconsole (e.g., Xbox™ and PlayStation™), an electronic dictionary, anelectronic key, a camcorder, and an electronic photo frame.

The electronic device may include at least one of various medicaldevices (e.g., various portable medical measuring devices (a bloodglucose monitoring device, a heart rate monitoring device, a bloodpressure measuring device, a body temperature measuring device, etc.), amagnetic resonance angiography (MRA), a magnetic resonance imaging (MRD,a computed tomography (CT) machine, and an ultrasonic machine), anavigation device, a global positioning system (GPS) receiver, an eventdata recorder (EDR), a flight data recorder (FDR), a vehicleinfotainment device, an electronic device for a ship (e.g., a navigationdevice for a ship, and a gyro-compass), avionics, security devices, anautomotive head unit, a robot for home or industry, an automatic tellermachine (ATM) in banks, point of sales (POS) devices in a shop, or anIoT device (e.g., a light bulb, various sensors, electric or gas meter,a sprinkler device, a fire alarm, a thermostat, a streetlamp, a toaster,a sporting goods, a hot water tank, a heater, a boiler, etc.).

The electronic device may include at least one of a part of furniture ora building/structure, an electronic board, an electronic signaturereceiving device, a projector, and various kinds of measuringinstruments (e.g., a water meter, an electric meter, a gas meter, and aradio wave meter). The electronic device may be a combination of one ormore of the aforementioned various devices. The electronic device mayalso be a flexible device. Further, the electronic device is not limitedto the aforementioned devices, and may include an electronic deviceaccording to the development of new technology.

Although the disclosure provides descriptions of an NR system, an LTEsystem, and an LTE-advanced (LTE-A) system, the disclosure may beapplied to a communication system having a structure similar to that ofthe above systems and other communication systems using a licensed bandand an unlicensed band, without any modification thereto. The disclosurerelates to a general wireless mobile communication system, and moreparticularly to a method for mapping a reference signal in a wirelessmobile communication system employing a multiple-access scheme usingmultiple carriers, such as orthogonal frequency-division multiple access(OFDMA).

A mobile communication system has evolved into a high-speed,high-quality wireless packet data communication system to provide dataand multimedia services. To this end, various standardizationorganizations, such as 3GPP, 3GPP2, IEEE, and the like, have beenworking on standardization of the 3rd evolved mobile communicationsystem to which a multiple-access scheme that uses multiple carriers canbe applied. Recently, various mobile communication standards such as LTEof 3GPP, ultra mobile broadband (UMB) of 3GPP2, 802.16m of IEEE, and thelike have been developed to support a high-speed and high-qualitywireless packet data communication system based on the multiple-accessscheme using multiple carriers.

Existing third-generation mobile communication system, such as LTE, UMB,and 802.16m, are based on a multi-carrier multiple access scheme. Inorder to improve transmission efficiency, such systems employ MIMO,multiple antennas and use a variety of technologies, such as abeamforming method, an AMC method, and a channel-sensitive schedulingmethod. The various technologies may enhance transmission efficiency andimprove system capacity performance through a method of concentratingtransmission power that is transmitted from multiple antennas oradjusting the amount of transmitted data, based on channel quality orthe like, and selectively transmitting, to a user, data having a goodchannel quality, or the like. Most of these schemes are operated basedon channel state information of a channel between a base station (BS),or g Node B (gNB), and a terminal (user equipment (UE) or mobile station(MS)), and thus the gNB or the UE may need to measure a channel statebetween the base station and the terminal. A channel state informationreference signal (CSI-RS) can be used. The above-mentioned gNB relatesto a downlink transmission/uplink reception device located at apredetermined place, and one gNB performs transmission and reception fora plurality of cells. In one mobile communication system, a plurality ofgNBs can be geographically dispersed, and each gNB can performtransmission and reception for a plurality of cells.

Existing 3rd and 4th generation mobile communication systems, such as,LTE, LTE-A, and the like, utilize MIMO technology, which executestransmission using a plurality of transmitting and receiving antennas toimprove the data transmission rate and the system capacity. The MIMOtechnology uses a plurality of transceiving antennas and may executetransmission by spatially dividing a plurality of information streams.Transmission through spatially dividing the plurality of informationstreams is referred to as spatial multiplexing. Generally, the number ofinformation streams to which spatial multiplexing is to be applied mayvary based on the number of antennas included in a transmitter and areceiver. The number of information streams to which spatialmultiplexing is to be applied is typically referred to as the rank of acorresponding transmission. When the MIMO technology is supported by theLTE-A Release 11 standards, spatial multiplexing is supported for 16transmission antennas or 8 reception antennas, and up to 8 ranks aresupported.

In the case of NR access technology, that is, a 5th-generation mobilecommunication system currently under discussion, the purpose of thesystem design is to support various services, such as an eMBB, an mMTC,and an URLLC. In the NR system, time and frequency resources areconfigured to be flexibly transmitted by enabling transmission of areference signal, which has conventionally been constantly transmitted,to be minimized and aperiodically performed.

Hereinafter, an electronic device will be described with reference tothe accompanying drawings. In the disclosure, the term “user” mayindicate a person using an electronic device or a device (e.g., anartificial intelligence electronic device) using an electronic device.

FIG. 1 illustrates a radio resource of one subframe and one resourceblock (RB), which is a minimum unit for downlink scheduling in the LTEsystem, according to an embodiment.

The radio resource illustrated in FIG. 1 is formed of a single subframeon a time axis and a single RB on a frequency axis. The radio resourceis formed of 12 subcarriers in the frequency domain, and 14 OFDM symbolsin the time domain, and thus, may have a total of 168 unique frequencyand time locations. In LTE, each unique frequency and time location ofFIG. 1 is referred to as a resource element (RE).

Through the radio resource illustrated in FIG. 1, a plurality ofdifferent types of signals may be transmitted as follows.

1. Cell-specific RS (CRS) 100: The CRS is a reference signalperiodically transmitted for all terminals belonging to one cell, andmay be commonly used by a plurality of terminals.

2. Demodulation reference signal 110 (DMRS): The DMRS is a referencesignal transmitted for a specific terminal, and is transmitted only whendata is transmitted to a corresponding terminal. The DMRS is formed of atotal of 8 DMRS ports. In LTE/LTE-A, ports from port 7 to port 14 areDMRS ports and ports maintain orthogonality therebetween in order toprevent the generation of interference therebetween using code divisionmultiplexing (CDM) or frequency division multiplexing (FDM).

3. Physical downlink shared channel 120 (PDSCH): The PDSCH is a datachannel for downlink transmission and is used for a base station totransmit traffic to a terminal. The PDSCH is transmitted using the RE,in which a reference signal is not transmitted in the data region 160 ofFIG. 1.

4. CSI-RS140: The CSI-RS is used to measure the channel state of areference signal transmitted for terminals belonging to one cell. Aplurality of CSI-RSs may be transmitted in a single cell.

5. Other control channels 130 (physical hybrid ARQ indicator channel(PHICH), physical control format indicator channel (PCFICH), andphysical downlink control channel (PDCCH)): Control channels are usedfor providing control information necessary for reception of a physicaldownlink shared channel (PDSCH) by a terminal or for transmitting anacknowledgement/negative acknowledgment (ACK/NACK) for operation ofhybrid automatic repeat request (HARQ) with respect to uplink datatransmission. Transmission is performed in a control region 150.

In addition to the signal, in the LTE system, muting may be set so thatterminals in a corresponding cell may receive a CSI-RS that istransmitted from another base station without interference. Muting maybe applied to a location where the CSI-RS may be transmitted, andgenerally, the terminal may skip the corresponding radio resources andreceive a traffic signal. In the LTE-A system, muting is also referredto as zero-power CSI-RS, due to the characteristics of muting, muting isapplied to the location of the CSI-RS and transmission power is nottransmitted.

In FIG. 1, a CSI-RS may be transmitted using some of the locationsexpressed as A, B, C, D, E, F, G, H, I, and J based on a number ofantennas that transmit a CSI-RS. Also, muting may be applied to some ofthe locations expressed as A, B, C, D, E, F, G, H, I, and J.Particularly, a CSI-RS may be transmitted using 2, 4, and 8 REs, basedon the number of antenna ports that execute transmission. For example,when the number of antenna ports is 2, a CSI-RS is transmitted throughhalf of a predetermined pattern in FIG. 1. When the number of antennaports is 4, a CSI-RS is transmitted through all of a predeterminedpattern. When the number of antennas ports is 8, a CSI-RS is transmittedusing two patterns. Conversely, muting is always executed based on asingle pattern. That is, muting may be applied to a plurality ofpatterns, but may not be applied to a portion of a single pattern whenthe location does not overlap a CSI-RS. However, when the location ofmuting and the location of a CSI-RS overlap, muting may be applied to aportion of a single pattern.

When a CSI-RS is transmitted with respect to two antenna ports, theCSI-RS may transmit signals of respective antenna ports through two REsthat are consecutive in the time axis, and the signal of each antennaport is distinguished by an orthogonal code. When a CSI-RS istransmitted with respect to four antenna ports, two more REs are used inaddition to the CSI-RS for two antenna ports, and the signals for thetwo antenna ports are additionally transmitted in the same manner.Likewise, the transmission of a CSI-RS associated with 8 antenna portsmay be executed. When a CSI-RS supporting 12 antenna ports and 16antenna ports, three CSI-RS transmission locations pertaining to fourexisting antenna ports are combined, or two CSI-RS transmissionlocations pertaining to eight antenna ports can be combined.

The terminal may receive allocation of CSI-IM (or interferencemeasurement resources (IMR)) together with the CSI-RS, in which theCSI-IM resource has the same resource structure and location as those ofthe CSI-RS supporting the 4 ports. The CSI-IM is a resource foraccurately measuring interference from an adjacent base station by aterminal that receives data from one or more base stations. For example,when the terminal wants to measure the amount of interference when anadjacent base station transmits data and the amount of interference whenan adjacent base station does not transmit data, the base station mayinclude a CSI-RS and two CSI-IM resources. The adjacent base station isconfigured to always transmit a signal in one CSI-IM, while the adjacentbase station is prevented from always transmitting a signal in the otherCSI-IM, so that the amount of interference of the adjacent base stationmay be effectively measured.

Table 1 described below shows a radio resource control (RRC) field forconfiguring a CSI-RS configuration. Particularly, Table 1 shows an RRCconfiguration for supporting a periodic CSI-RS within the CSI process.

TABLE 1 CSI-RS config CSI-IM config CQI report config Etc Number ofantenna resource config: periodic: mode, Pc ports time and frequencyresource, periodicity, codebook resource config: position in a offsetetc subset time and frequency subframe aperiodic: mode etc restric-position in a subframe config: PMI/RI report tion subframe periodicityand RI reference CQI subframe config: subframe offset processperiodicity and subframepattem subframe offset QCL-CRS- info(QCL typeB): CRS information for CoMP

Configuring channel state reporting based on a periodic CSI-RS in a CSIprocess may be classified into four types, as shown in Table 1. CSI-RSconfig is for configuring frequency and time positions of a CSI-RS RE.The number of ports that the corresponding CSI-RS has is configured byconfiguring the number of antennas. Resource config configures an REposition within an RB, and Subframe config configures a period and anoffset of a subframe. Table 2 is a table for configuring Resource configand Subframe config, which are currently supported by LTE.

TABLE 2 CSI reference Number of CSI reference signals configured signal1 or 2 4 8 con- n_(s) n_(s) n_(s) figuration (k′, l′) mod 2 (k′, l′) mod2 (k′, l′) mod 2 Frame 0 (11, 4) 0 (11, 4) 0 (11, 4) 0 structure 1 (9,4) 0 (9, 4) 0 (9, 4) 0 type 1 2 (10, 4) 1 (10, 4) 1 (10, 4) 1 and 2 3(9, 4) 1 (9, 4) 1 (9, 4) 1 4 (5, 4) 0 (5, 4) 0 5 (3, 4) 0 (3, 4) 0 6 (4,4) 1 (4, 4) 1 7 (3, 4) 1 (3, 4) 1 8 (8, 4) 0 9 (6, 4) 0 10 (2, 4) 0 11(0, 4) 0 12 (7, 4) 1 13 (6, 4) 1 14 (1, 4) 1 15 (0, 4) 1 Frame 16(11, 1) 1 (11, 1) 1 (11, 1) 1 structure 17 (10, 1) 1 (10, 1) 1 (10, 1) 1type 2 18 (9, 1) 1 (9, 1) 1 (9, 1) 1 only 19 (5, 1) 1 (5, 1) 1 20 (4, 1)1 (4, 1) 1 21 (3, 1) 1 (3, 1) 1 22 (8, 1) 1 23 (7, 1) 1 24 (6, 1) 1 25(2, 1) 1 26 (1, 1) 1 27 (0, 1) 1

TABLE 3 CSI-RS- CSI-RS CSI-RS subframe SubframeConfig periodicityT_(CSI-RS) offset Δ_(CSI-RS) I_(CSI-RS) (Subframes) (subframes)  0-4 5I_(CSI-RS)  5-14 10 I_(CSI-RS) − 5 15-34 20 I_(CSI-RS) − 15 35-74 40I_(CSI-RS) − 35 75-154 80 I_(CSI-RS) − 75

The terminal is capable of checking frequency and time positions, aperiod, and an offset via Table 2 and Table 3. Quasi-colocated(Qcl)-CRS-info configures quasi co-position information for coordinatedmulti-point (CoMP). CSI-IM config is for configuring frequency and timepositions of CSI-IM for interference measurement. Since CSI-IM is alwaysconfigured based on 4 ports, it is not necessary to configure the numberof antenna ports, and Resource config and Subframe config are configuredin the same way as CSI-RS. CQI report config exists to configure how toreport a channel state, by using a corresponding CSI process. PeriodicCSI reporting setting, aperiodic CSI reporting setting, PMI/RI reportsetting, RI reference CSI process configuration, subframe patternconfiguration, and the like are also included.

For interference measurement and channels received by the terminal, asubframe pattern is for configuring a measurement subframe subset forsupporting interference measurement and a channel having differenttemporal characteristics. The measurement subframe subset was firstintroduced for the enhanced inter-cell interference coordination (eICIC)to employ other interference characteristics of an almost-blank subframe(ABS) and a non-ABS general subframe so as to perform estimation. Themeasurement subframe subset was developed into a form that enablesmeasurement by configuring two IMRs in order to measure differentchannel characteristics between a subframe that is dynamicallyswitchable from downlink to uplink and a subframe that always operatesas downlink in enhanced interference mitigation and traffic adaptation(eIMTA). Tables 4 and 5 show the measurement subframe subset forsupporting eICIC and eIMTA.

TABLE 4 CQI-ReportConfig-r10 ::= SEQUENCE {  cqi-ReportAperiodic-r10 CQI-ReportAperiodic-r10 OPTIONAL, -- Need ON  nomPDSCH-RS-EPRE-OffsetINTEGER (−1..6),  cqi-ReportPeriodic-r10  CQI-ReportPeriodic-r10OPTIONAL, -- Need ON  pmi-RI-Report-r9  ENUMERATED {setup} OPTIONAL, --Cond PMIRIPCell  csi-SubframePatternConfig-r10  CHOICE {   release NULL,   setup  SEQUENCE {    csi-MeasSubframeSet1-r10  MeasSubframePattern-r10,    csi-MeasSubframeSet2-r10  MeasSubframePattern-r10   }  } OPTIONAL -- Need ON }

TABLE 5 CQI-ReportConfig-v1250 ::= SEQUENCE { csi-SubframePatternConfig-r12  CHOICE {   release  NULL,   setup SEQUENCE {    csi-MeasSubframeSets-r12    BIT STRING (SIZE (10))   }  } OPTIONAL, -- Need ON  cqi-ReportBoth-v1250   CQI-ReportBoth-v1250  OPTIONAL,  -- Need  ON  cqi-ReportAperiodic-v1250CQI-ReportAperiodic-v1250 OPTIONAL, -- Need ON  altCQI-Table-r12ENUMERATED { allSubframe, csi-SubframeSet1, csi-SubframeSet2, spare1} OPTIONAL  -- Need  OP }

An eICIC measurement subframe subset supported by LTE is configuredusing csi-MeasSubframeSet1-r10 and csi-MeasSubframeSet2-r10.MeasSubframePattern-r10 referred to by a corresponding field is shown inTable 6 set forth below.

TABLE 6 -- ASN1START MeasSubframePattern-r10 ::= CHOICE { subframePatternFDD-r10 BIT STRING (SIZE (40)),  subframePatternTDD-r10CHOICE {   subframeConfig1-5-r10 BIT STRING (SIZE (20)) ,  subframeConfig0-r10 BIT STRING (SIZE (70))   subframeConfig6-r10 BITSTRING (SIZE (60)),   . . .  },  . . . } -- ASN1STOP

Most significant bit (MSB) on the left in the field indicates subframe#0, and when a bit value is 1, it is indicated that a correspondingsubframe is included in a measurement subframe subset. Unlike the eICICmeasurement subframe subset, in which subframe sets are configuredthrough respective fields, in the eIMTA measurement subframe set using asingle field, a bit value of 0 indicates that a corresponding subframeis included in a first subframe set, and a bit value of 1 indicates thata corresponding subframe is included in a second subframe set.Therefore, there is a difference in that, in the eICIC, correspondingsubframes may not be included in two subframe sets, but in the eIMTAsubframe set, corresponding subframes should always be included one oftwo subframe sets.

In addition, there is a power ratio between a PDSCH and a CSI-RS RE(which is referred to as Pc) which is required for a terminal togenerate a channel state report, and codebook subset restriction forconfiguring which codebook is to be used. Pc and codebook subsetrestriction are configured by a p-C-AndCBSRList field including twoP-C-AndCBSR fields shown in Table 8 in a list form, and each fieldrefers to a configuration for each subframe subset.

TABLE 7 CSI-Process-r11 :: = SEQUENCE {  ...  p-C-AndCBSRList-r11SEQUENCE (SIZE (1..2)) OF P-C-AndCBSR-r11,  ... }

TABLE 8 P-C-AndCBSR-r11 ::= SEQUENCE {  p-C-r11 INTEGER (−8..15), codebookSubsetRestriction-r11  BIT STRING }

P_(C) may be defined by the mathematical Equation (1) below, and a valuebetween −8 and 15 dB may be specified.

$\begin{matrix}{P_{C} = \frac{{PDSCH}\mspace{14mu}{EPRE}}{{CSI} - {{RS}\mspace{14mu}{EPRE}}}} & (1)\end{matrix}$

The base station may variably adjust CSI-RS transmission power forvarious purposes, such as improving a channel estimation accuracy, etc.,and the terminal may figure out how low or high the transmission powerto be used for data transmission is, compared with the transmissionpower used for channel estimation, using the provided Pc. Even if thebase station varies the CSI-RS transmission power, the terminal may beable to calculate an accurate CQI and report the calculated CQI to thebase station.

In a cellular system, the base station should transmit a referencesignal to the terminal in order to measure a downlink channel state. Inthe LTE system of the 3GPP, the terminal measures a channel statebetween the base station and the terminal by using a CSI-RS or a CRStransmitted by the base station. In association with the channel state,several factors need to be fundamentally considered, and the amount ofinterference in a downlink may be included therein. The amount ofinterference in a downlink may include an interference signal generatedby an antenna that belongs to an adjacent base station's thermal noise,and the like, which is important when a terminal determines the channelstate of the downlink.

When a base station having one transmission antenna transmits a signalto a terminal having one reception antenna, the terminal may have todetermine the amount of energy per symbol and the amount of interferencein order to determine an interference-to-symbol energy ratio (Es/Io),wherein the amount of energy per symbol is received in the downlink byusing a reference signal received from the base station, and the amountof interference is to be concurrently received in intervals forreception of corresponding symbols. The determined Es/Io is convertedinto a data transmission rate or a value corresponding thereto, and isprovided to the base station in the form of a CQI, so that the basestation may determine the data transmission rate at which to performtransmission to the terminal.

In the case of the LTE system, the terminal feeds back informationassociated with a channel state of a downlink to the base station, sothat the base station utilizes the same for downlink scheduling. Thatis, the terminal measures a reference signal transmitted in the downlinkby the base station, and feeds back information extracted therefrom tothe base station in a form defined by the LTE standard. There are threemajor types of information that the terminal feeds back in LTE.

-   -   RI: The number of spatial layers that the terminal may receive        in the current channel state.    -   Precoder matrix indicator (PMI): An indicator for a precoding        matrix preferred by the terminal in the current channel state.    -   CQI: The maximum data rate that the terminal may receive in the        current channel state. The CQI may be replaced with a        signal-to-interference plus noise ratio (SINR) that may be        utilized similar to the maximum data rate, a maximum error        correction-coding rate, a modulation scheme, data efficiency per        frequency, and the like.

The RI, PMI, and CQI are interrelated. For example, a precoding matrixsupported in LTE/LTE-A may be defined to be different for each rank.Therefore, a PMI value when the RI has a value of 1 and a PMI value whenthe RI has a value of 2 are interpreted differently even if the valuesthereof are the same. Also, when the terminal determines the CQI, it isassumed that the PMI value and the rank value that the terminal itselfhas provided to the base station are applied to the base station. Thatis, when the terminal provides RI₁₃X, PMI_Y, and CQI_Z to the basestation, the terminal may receive data at a data transmission ratecorresponding to CQI_Z when the rank is RI_X and precoding is PMI_Y.When the terminal calculates a CQI, the terminal assumes thetransmission scheme to be executed with respect to the base station sothat the terminal may obtain optimal performance when the terminalactually executes transmission using the corresponding transmissionscheme.

In LTE, periodic feedback of a terminal may be configured to one of thefollowing four feedback modes (or reporting modes), based on informationthat is included.

-   -   Reporting mode 1-0 (wideband CQI with no PMI): RI, broadband        (wideband) CQI (wCQI)    -   Reporting mode 1-1 (wideband CQI with single PMI): RI, wCQI, PMI    -   Reporting mode 2-0 (subband CQI with no PMI): RI, wCQI,        narrowband (subband) CQI (sCQI)    -   Reporting mode 2-1 (subband CQI with single PMI): RI, wCQI,        sCQI, PMI

The feedback timing of each piece of information for the four feedbackmodes is determined by a value, such as N_(pd), N_(OFFSET, CQI), M_(RI),and N_(OFFSET, RI), transmitted through a higher-layer signal. Infeedback mode 1-0, the transmission period of a wCQI is N_(pd), andfeedback timing may be determined based on a subframe offset value ofN_(OFFSET, CQI). Further, the transmission period of RI isN_(pd)-N_(RI), and an offset is N_(OFFSET, CQI)+N_(OFFSET, RI).

FIG. 2 is a diagram of feedback timing 200 of RI and wCQI when N_(pd)=2,M_(RI)=2, N_(OFFSET, CQI)=1, and N_(OFFSET, RI)=−1, according to anembodiment. In FIG. 2, each timing indicates a subframe index.

Although feedback mode 1-1 has the same feedback timing as that of mode1-0, it is different in that a wCQI is transmitted together with a PMIat a wCQI transmission timing.

In feedback mode 2-0, a feedback period for sCQI is N_(pd) and an offsetvalue is N_(OFFSET, CQI). Further, a feedback period for wCQI isH·N_(pd), and an offset value is N_(OFFSET, CQI), which is the same asthat of sCQI. Here, H=J·K+1, in which K is transmitted through ahigher-layer signal, and J is a value determined by a system bandwidth.

A value of J with respect to a 10 MHz system is defined as 3.Accordingly, a wCQI is transmitted every H transmissions of an sCQI,instead of the sCQI. The period of an RI corresponds to M_(RI)·H·N_(pd)subframes, and the offset thereof is N_(OFFSET,CQI)+N_(OFFSET,RI).

FIG. 3 is a diagram of feedback timing 300 of RI, sCQI, and wCQI whenN_(pd)=2, M_(RI)=2, J=3(10 MHz), K=1, N_(OFFSET, CQI)=1, andN_(OFFSET, RI)=−1, according to an embodiment.

Although feedback mode 2-1 has the same feedback timing as that of mode2-0, it is different in that a wCQI is transmitted together with a PMIat a wCQI transmission timing.

The above-described feedback timing corresponds to when the number ofCSI-RS antenna ports is less than or equal to 4. When a terminal isassigned with a CSI-RS associated with 8 antenna ports, two types of PMIinformation need to be fed back, unlike the feedback timing. Feedbackmode 1-1 with respect to 8 CSI-RS antenna ports is divided into twosubmodes. In a first submode, an RI is transmitted together with firstPMI information, and second PMI information is transmitted together witha wCQI. A feedback period and an offset with respect to the wCQI and thesecond PMI are defined as N_(pd), N_(OFFSET, CQI), and a feedback periodand an offset value for the RI and the first PMI information are definedas M_(RI)·N_(pd), N_(OFFSET, CQI)+N_(OFFSET, RI), respectively. Here,when a precoding matrix corresponding to the first PMI is W₁ and aprecoding matrix corresponding to the second PMI is W₂, a terminal and abase station share information indicating that the precoding matrixpreferred by the terminal is determined to be W₁*W₂.

When feedback mode 2-1 is for eight CSI-RS antenna ports, feedback ofprecoding type indicator (PTI) information is added. PTI is fed backwith RI, and a period thereof corresponds to M_(R)I·H·M_(pd), and anoffset thereof is defined as N_(OFFSET, CQI)+N_(OFFSET, RI). When thePTI is 0, a first PMI, a second PMI, and a wCQI are all fed back. ThewCQI and the second PMI are transmitted together at an identical timing,the period is N_(pd), and an offset is N_(OFFSET, CQI). Also, the periodof the first PMI corresponds to H′·N_(pd), and the offset isN_(OFFSET, CQI). Here, H′ is transmitted through a higher-layer signal.Conversely, when the PTI is 1, the PTI is transferred together with anRI, and wCQI and a second PMI are transmitted together, and sCQI isadditionally fed back at another timing. The first PMI is nottransmitted. The period and offset of the PTI and the RI are identicalto the case in which the PTI is 0, and the sCQI is defined to have aperiod of N_(pd) and an offset of N_(OFFSET, CQI). Also, the wCQI andthe second PMI are fed back with a period of H·N_(pd) and an offset ofN_(OFFSET, CQI). H is identical to when the number of CSI-RS antennaports is 4.

FIG. 4 is a diagram of feedback timing 400 when PTI=0 and N_(pd)=2,M_(RI)=2, J=3 (10 MHz), K=1, H′=3, N_(OFFSET, CQI)=1, andN_(OFFSET, RI)=−1, according to an embodiment.

FIG. 5 is a diagram of feedback timing 500 when PTI=1 and N_(pd)=2,M_(RI)=2, J=3(10 MHz), K=1, H′=3, N_(OFFSET, CQI)=1, andN_(OFFSET, RI)=−1, according to an embodiment.

FIG. 6 is a diagram of a periodic channel state reporting time point fora CSI-RS port of 12 ports or more for a 2-D array antenna supported byLTE Rel-13 and Rel-14, according to an embodiment.

LTE Rel-13 and Rel-14 support a non-precoded (NP) CSI-RS to support 12or more CSI-RS ports for 2-D array antennas. The NP CSI-RS supports 8,12, 16 or more CSI-RS ports by using positions for the existing CSI-RSin one subframe. The corresponding field is configured toCSI-RS-ConfigNZP-EMIMO. A terminal may identify a position for a CSI-RSresource and may receive a CSI-RS, by using the same. Further, in abeamformed (BF) CSI-RS, individual CSI-RS resources are combined andused as the BF CSI-RS, by using csi-RS-ConfigNZPIdListExt-r13 andcsi-IM-ConfigIdListExt-r13, in which the number of CSI-RS ports, asubframe, and a codebook subset restriction may all be different in eachof the individual CSI-RS resources.

In order to support a 2D antenna in the NP CSI-RS, a new 2D codebook isrequired, which may vary depending on an oversampling factor, a codebookconfiguration, and a dimension-specific antenna. According to analysisof PMI bits of the 2D codebook, in the case of bits for i₂ (W2)reporting, it is possible to use an existing channel state reportingmethod, in which all of the bits are 4 bits or less. However, in thecase of i_(1,1) and i_(1,2), as shown in Table 9 and Table 10, PMI bitsare increased with respect to supporting N₁, N₂, O₁, O₂, andcodebookConfig, as follows.

TABLE 9 (N₁, N₂) (O₁, _O₂) combinations (8, 1) (4, —) (8, —) (2, 2) (4,4) (8, 8) (2, 3) {(8, 4) (8, 8)} (3,2) {(8, 4) (4, 4)} (2, 4) {(8, 4)(8, 8)} (4, 2) {(8, 4) (4, 4)}

TABLE 10 Config = 1 Config = 2, 3, 4 (N₁, N₂) (O₁, O₂) W_(1,1)/W_(1,2)bits (O₁, O₂) W_(1,1)/W_(1,2) bits (N₁, N₂) (O₁, O₂) W_(1,1)/W_(1,2)bits (O₁, O₂) W_(1,1)/W_(1,2) bits (8, 1) (4, −) 5 + 2(additional (8, −)6 + 2 (8, 1) (4, −) 4 + 2 (8, −) 5 + 2 for rank 3, 4) (2, 2) (4, 4) 3 +⅓ (8, 8) 4 + ¼ (2, 2) (4, 4) 2 + ½ (8, 8) 3 + ⅓ (2, 3) (8, 4) 4 + ¼ (8,8) 4 + ⅕ (2, 3) (8, 4) 3 + ⅓ (8, 8) 3 + ¼ (3, 2) (8, 4) 5 + ⅓ (4, 4) 4 +⅓ (3, 2) (8, 4) 4 + ½ (4, 4) 3 + ½ (2, 4) (8, 4) 4 + ¼ (8, 8) 4 + ⅕ (2,4) (8, 4) 3 + ⅓ (8, 8) 3 + ¼ (4, 2) (8, 4) 5 + ⅓ (4, 4) 4 + ⅓ (4, 2) (8,4) 4 + ½ (4, 4) 3 + ½

Based on the above table, when (N₁, N₂, O₁, O₂)=(2, 4, 8, 8) and Configis one, i₁ is required in order to transmit a maximum of 10 bits. WhenPUCCH format 2, used for existing periodic channel state reporting, upto 13 bits of Reed-Muller codes used for channel coding can betransmitted. However, when an extended cyclic prefix (CP), since HARQACK/NACK of two bits should be supported, an actual payload sizetransmittable in a normal CP situation is 11 bits. In order to supportthe payload size, in both a wideband CQI mode and a subband CQI mode, achannel state is reported using the three independent CSI reporting timepoints, as shown in FIG. 6.

LTE may support aperiodic feedback, in addition to periodic feedback ofthe terminal. When a base station desires to obtain aperiodic feedbackinformation of a predetermined terminal, the base station may configurean aperiodic feedback indicator included in downlink control information(DCI) for uplink data scheduling of the corresponding terminal toexecute predetermined aperiodic feedback, and executes uplink datascheduling of the corresponding terminal. When the terminal receives, atan n^(th) subframe, an indicator that is configured to execute aperiodicfeedback, the terminal executes uplink transmission by includingaperiodic feedback information in data transmission at an n+k^(th)subframe. Here, k is a parameter defined in the LTE Release 11 standard,which is 4 in the case of frequency-division duplexing (FDD), and may bedefined as shown in Table 11 in the case of time-division duplexing(TDD).

TABLE 11 TDD UL/DL subframe number n Configuration 0 1 2 3 4 5 6 7 8 9 0— — 6 7 4 — — 6 7 4 1 — — 6 4 — — — 6 4 — 2 — — 4 — — — — 4 — — 3 — — 44 4 — — — — — 4 — — 4 4 — — — — — — 5 — — 4 — — — — — — — 6 — — 7 7 5 —— 7 7 —

When aperiodic feedback is configured, the feedback information mayinclude an RI, PMI, and CQI in the same manner as the periodic feedback,and the RI and the PMI may not be fed back on the basis of a feedbackconfiguration. The CQI may include both a wCQI and an sCQI, or mayinclude only wCQI information.

LTE may provide a codebook subsampling function for periodic channelstate reporting. In LTE, periodic feedback of the terminal may betransmitted to a base station through a physical uplink control channel(PUCCH). The amount of information that may be transmitted through aPUCCH at one time is limited, and thus, various feedback objects, suchas, an RI, a wCQI, an sCQI, a PMI1, a wPMI2, an sPMI2, and the like, maybe transmitted through a PUCCH after subsampling, or two or more piecesof feedback information may be jointly encoded and transmitted through aPUCCH. When the number of CSI-RS ports configured by a base station is8, an RI and a PMI1 reported in submode 1 of PUCCH mode 1-1 may bejointly encoded as shown in Table 12 below.

Referring to Table 12, an RI formed of 3 bits and a PMI1 formed of 4bits are jointly encoded to have a total of 5 bits. In submode 2 ofPUCCH mode 1-1, as shown in Table 13 below, a PMI1 formed of 4 bits anda PMI2 formed of another 4 bits are jointly encoded to form a total of 4bits of information. Since a subsampling scale is larger than submode 1(subsampling 7 bits to 5 bits in submode 1, and subsampling 8 bits to 4bits in submode 2), more precoding factors may not be reported. When thenumber of CSI-RS ports configured by a base station is 8, a PMI2reported in PUCCH mode 2-1 may be subsampled as shown in Table 11. Forexample, referring to Table 11, PMI2 is reported to have 4 bits when theassociated RI is 1. However, when the associated RI is a value greaterthan or equal to 2, a differential CQI for a second code word needs tobe additionally reported, and thus the PMI2 is subsampled to 2 bits ofinformation and reported.

TABLE 12 Value of joint encoding of RI Codebook and the first PMII_(RI/PMI1) RI index i₁  0-7 1 2I_(RI/PMI1)  8-15 2 2( I_(RI/PMI1) −8)16-17 3 2( I_(RI/PMI1) − 16) 18-19 4 2( I_(RI/PMI1) − 18) 20-21 5 2(I_(RI/PMI1) − 20) 22-23 6 2( I_(RI/PMI1) − 22) 24-25 7 2( I_(RI/PMI1) −24) 26 8 0 27-31 reserved NA

TABLE 13 Relationship between the Relationship between the first PMIvalue and second PMI value and codebook index i₁ codebook index i₂ Valueof the Value of the first Codebook second Codebook total RI PMI I_(PMI1)index i₁ PMI I_(PMI2) index i₂ #bits 1 0-7 2I_(PMI1) 0-1 2I_(PMI2) 4 20-7 2I_(PMI1) 0-1 I_(PMI2) 4 3 0-1 2I_(PMI1) 0-7 4└I_(PMI2)/4┘ +I_(PMI2) 4 4 0-1 2I_(PMI1) 0-7 I_(PMI2) 4 5 0-3 I_(PMI1) 0 0 2 6 0-3I_(PMI1) 0 0 2 7 0-3 I_(PMI1) 0 0 2 8 0 0 0 0 0

TABLE 14 Relationship between the second PMI value and codebook index i₂RI Value of the second PMI I_(PMI2) Codebook index i₂ 1 0-15 I_(PMI2) 20-3  2I_(PMI2) 3 0-3  8 · └I_(PMI2)/2┘ + (I_(PMI2) mod 2) + 2 4 0-3 2I_(PMI2) 5 0 0 6 0 0 7 0 0 8 0 0

FIG. 7 is a diagram in which data, such as eMBB, URLLC, and mMTC, whichcorrespond to services considered in the NR system, is allocated in afrequency-time resource together with a forward-compatible resource(FCR), according to an embodiment.

When eMBB 700 and mMTC 710 are allocated to a specific frequency bandand transmitted, if URLLC data 720 is generated and required to betransmitted, the eMBB and mMTC empty pre-allocated parts, and the URLLCdata is transmitted. Among the services, since a short delay time isparticularly important for URLLC, the URLLC data may be allocated to aportion of the resources to which the eMBB has been allocated, and maybe transmitted, and information about the eMBB resources may be providedto the terminal in advance. To this end, the eMBB data may not betransmitted in a frequency-time resource in which the eMBB data and theURLLC data overlap, and therefore the transmission performance of theeMBB data may be lowered. That is, eMBB data transmission failure due toURLLC allocation may occur. The length of a transmission time interval(TTI) used for URLLC transmission may be shorter than the TTI lengthused for eMBB or mMTC transmission.

In a procedure of accessing a wireless communication system by theterminal, a synchronization signal is used to acquire synchronizationwith a cell in a network. More specifically, the synchronization signalrefers to a reference signal transmitted for time-and-frequencysynchronization and cell searching by a base station upon initial accessof the terminal, and a signal, such as a primary synchronization signal(PSS) or a secondary synchronization signal (SSS), may be transmittedfor synchronization in LTE.

FIG. 8 is a diagram in which a synchronization signal is transmitted inthe 5G communication system considered in the present disclosure,according to an embodiment.

In FIG. 8, a synchronization signal 801 may be transmitted at eachperiod at a predetermined interval 804 on the time axis 802. Thesynchronization signal 801 may also be transmitted within a constantsynchronization signal transmission bandwidth 805 on the frequency axis803. In order to indicate a cell number (Cell ID) by using thesynchronization signal, a special sequence may be mapped to a subcarrierwithin the transmission bandwidth 805. The cell number may be mappedusing a combination of one or multiple sequences, and therefore theterminal may detect the number of the cell that the terminal desires toaccess by detecting the sequence used for the synchronization signal.The sequence used for the synchronization signal may be a sequencehaving a constant amplitude zero auto correlation (CAZAC)characteristic, such as a zadoff-chu sequence or a golay sequence, ormay be a pseudo-random noise sequence, such as an m-sequence or a goldsequence. It is assumed that the above-mentioned synchronization signalis used for a synchronization signal, but the disclosure is not limitedto any specific signal.

The synchronization signal 801 may be configured using one OFDM symbolor a plurality of OFDM symbols. When the synchronization signal 801 isconfigured using a plurality of OFDM symbols, a sequence for a pluralityof different synchronization signals may be mapped to each OFDM symbol.For example, as in LTE, three zadoff-chu sequences may be used togenerate a PSS, and a gold Sequence may be used to generate an SSS. APSS of one cell may have three different values according to thephysical layer cell ID of the cell, and the three cell IDs in one cellID group correspond to different PSSs. Therefore, the terminal maydetect the PSS of the cell to identify one cell ID group among threecell ID groups supported by LTE. The terminal additionally detects anSSS among 168 cell IDs, reduced from 504 cell IDs, via the ID groupidentified through the PSS, so as to determine the cell ID to which thecorresponding cell belongs.

The terminal acquires a cell number in synchronization with a cellwithin the network, and finds a cell frame timing. Once the cell frametiming is successfully found, the terminal should receive important cellsystem information. The important cell system information is informationthat is repeatedly broadcasted by the network, and corresponds toinformation that the terminal should generally know in order to accessthe cell and properly operate within the cell. In LTE, systeminformation is transmitted over two different transport channels, inwhich a limited amount of system information, called a masterinformation block (MIB) is transmitted using a physical broadcastchannel (PBCH), and a main part of the system information, correspondingto a system information block (SIB), is transmitted using a PDSCH. Morespecifically, in the LTE system, the system information included in theMIB includes a downlink transmission bandwidth, PHICH configurationinformation, and a system frame number (SFN).

FIG. 9 is a diagram in which a PBCH is transmitted in the 5Gcommunication system, according to an embodiment. In FIG. 9, a PBCH 901may be transmitted periodically at a predetermined interval 904 on thetime axis 902. The PBCH 901 may also be transmitted within apredetermined PBCH transmission bandwidth 905 on the frequency axis 903.In order to improve coverage, the PBCH may transmit the same signal atthe predetermined interval 904, and the terminal may combine thetransmitted signals and receive the same. Further, a plurality ofantenna ports are used for application of a transmission technique, suchas transmit diversity (T×D) and one DMRS port-based precoder cycling,and a diversity gain may thus be obtained without additional informationon the transmission technique used by the reception end. It is assumedthat the above-mentioned PBCH is used for a PBCH, but the disclosure isnot limited to any specific structure.

Similar to the current LTE system, the PBCH 901 may be configured usinga plurality of OFDM symbols at resources in a time-frequency domain, ormay be scattered over resources in a time-frequency domain. The terminalshould receive and decode the PBCH in order to receive systeminformation, and the terminal performs channel estimation on the PBCH byusing a CRS in the LTE system.

FIG. 10 is a diagram of services that are multiplexed in respective timeand frequency resources in the NR system, according to an embodiment. Abase station may allocate CSI-RSs to all (or a plurality of) bands inorder to secure initial channel state information for a terminal. Thefull-band or multiple-band CSI-RS 1000 requires a large amount ofreference signal overhead, and it may thus be disadvantageous foroptimizing system performance. However, when there is no previouslysecured information, full-band or multiple-band CSI-RS may be necessary.

After transmission of the full-band or multiple-band CSI-RS, eachservice may be provided with different requirements for each service,and the accuracy of necessary channel state information and updatethereof may also be changed. Therefore, after securing the initialchannel state information, the base station may trigger a subband CSI-RS1010 for each service in a corresponding band according to the necessityfor each service. Although FIG. 10 illustrates the transmission of aCSI-RS for each service at one time point, it is also possible thatCSI-RSs for a plurality of services are transmitted as needed.

In comparison with the above-mentioned CSI-RS transmission and CSIreporting setting of LTE, a CSI-RS transmission and a CSI reportingsetting which are supported by NR may have different forms. NR isdifferent from LTE in that it supports a more flexible CSI reportingsetting than LTE through a resource setting, a CSI measurement setting,and a CSI reporting setting, which are necessary in order to supportchannel state reporting.

FIG. 11 is a diagram of a resource setting, a CSI measurement setting,and a CSI reporting setting which are necessary for supporting channelstate reporting in NR, according to an embodiment.

The resource setting, the CSI measurement setting, and the CSI reportingsetting may include configuration information as described below.

-   -   CSI reporting setting 1100: Turning on/off of report parameters        (e.g., RI, PMI, CQI, etc.) required for channel state reporting        may be configured. In addition, a channel state report type may        be configured (e.g., configuration may be performed according to        Type I (channel state reporting having a low resolution and an        implicit report type) or Type II (channel state reporting having        a high resolution, and a type of explicitly reporting an        eigenvector, a covariance matrix, etc., by using linear        combination-type channel state reporting). Specifically, a CSI        reporting setting (whether to report RI, PMI, CQI, BI, CRI, or        the like (an individual configuration or combined        configuration)), the reporting method (periodic, aperiodic, and        semi-persistent reporting are available, in which the aperiodic        and semi-persistent reporting may be configured as one        parameter), codebook configuration information, a PMI type        (full-band or partial-band), a channel state report type        (implicit/explicit or Type I/Type II), a channel quality report        type (CQI/RSRP), and a resource setting for channel state        reporting may be supported.    -   Resource setting 1110: Resource setting corresponds to a        configuration including configuration information relating to a        reference signal required for channel state measurement. A        CSI-RS resource for channel measurement and an interference        measurement resource (CSI-IM) for interference measurement may        be configured via resource setting, and a plurality of resource        settings may exist for this purpose. In addition, a transmission        type of a corresponding reference signal (periodic, aperiodic,        and semi-persistent transmission), a transmission period and        offset of the reference signal, and the like can be configured.    -   CSI measurement setting 1120: CSI measurement setting        corresponds to configuration of mapping or connection between        the CSI reporting setting and the resource setting. When there        are N CSI reporting settings and M resource settings, L links        establishing the mapping between these multiple CSI reporting        settings and resource settings may be included in the CSI        measurement setting. An association configuration between the        reference signal configuration and a reporting time point (e.g.,        when the reference signal is to be transmitted to n subframes or        slots, the reporting time point may be configured using        parameters, such as D0-0, D1-0, D2-1, D3-2 and D3-3, and the        reporting time point may be defined as n+D0-0 accordingly) may        also be configured via CSI measurement setting.

In addition to periodic and aperiodic channel state reporting supportedby LTE, the NR supports semi-persistent reference signal transmissionand channel state information. The periodic and semi-persistent channelstate information of the NR may not support subband reporting among theabove-mentioned reporting modes. The PUCCH used in the periodic andsemi-persistent channel state reporting has a limited amount of reportsthat may be transmitted. Therefore, as mentioned above, in LTE, theterminal may be allowed to select some subbands in the bandwidth andreport channel state information relating to the subbands. However,since a report on such selective subbands contains very limitedinformation, the usefulness of this information may be minimal.Therefore, the lack of support for such reporting may result in reducedcomplexity of the terminal and increased efficiency of the reporting. Inaddition, since subband reporting is not supported, a PMI may not bereported, or only one PMI corresponding to a wideband or partial bandmay be transmitted in periodic channel state information reporting inthe NR.

The aperiodic channel state information reporting of the NR may supportthe following reporting modes.

-   -   Reporting mode 1-2 (wideband CQI with multiple PMI): RI,        broadband (wideband), CQI (wCQI), a plurality of broadband and        narrowband PMIs    -   Reporting mode 2-0 (subband CQI with no PMI): RI, wCQI, and a        narrowband (subband) CQI (sCQI) of a band selected by the        terminal    -   Reporting mode 2-2 (subband CQI with multiple PMIs): RI, wCQI,        sCQI, a plurality of broadband and narrowband PMIs    -   Reporting mode 3-0 (subband CQI with no PMI): RI, wCQI, and a        narrowband (subband) CQI (sCQI) of the full band    -   Reporting mode 3-2 (subband CQI with multiple PMIs): RI, wCQI, a        narrowband (subband) CQI (sCQI) of the full band, and a        plurality of broadband and narrowband PMIs

Similar to cyclic channel state reporting, report modes 2-0 and 2-2correspond to a type of selecting and reporting of subbands of theportion of the bandwidth of the terminal, and may not be supported in NRdue to the low efficiency of the reporting. In the periodic channelstate reporting in LTE, a reporting mode can be determined using the CQIsetting and the PMI/RI report setting of a channel state reporting modesetting of the corresponding channel, and a channel state reporting modecan be directly configured when using aperiodic channel state reporting.In the NR, the PMI/RI report setting and the CQI reporting setting maybe provided in the above-mentioned CSI reporting settings, respectively.

As mentioned above, the NR supports two types of channel state reportinghaving a low spatial resolution and a high spatial resolution. Tables 15and 16 and Tables 17 and 18 below show two types of channel statereporting and the reporting overhead required for each report type.Particularly, Table 15 indicates Type 1 channel state reporting, Table16 indicates Type 2 channel state reporting, Table 17 indicates theoverhead necessary for Type 1 channel state reporting, and Table 18indicates the overhead necessary for Type 2 channel state reporting.

TABLE 15  In the case of two antenna ports, the NR supports a Type 1code- book described below.${W \in {\left\{ {{\frac{1}{\sqrt{2}}\begin{bmatrix}1 \\e^{j\frac{\pi\; n}{2}}\end{bmatrix}},{n = 0},1,2,3} \right\}\mspace{14mu}{for}}}\mspace{14mu}$${rank}\text{-}1\mspace{14mu}{and}\mspace{14mu}\left\{ {{\frac{1}{2}\begin{bmatrix}1 & 1 \\j^{n} & {- j^{n}}\end{bmatrix}},{n = 0},1} \right\}\mspace{14mu}{for}\mspace{14mu}{rank}\text{-}2$ In the case of four or more antenna ports, the NR supports channelstate reporting for rank 1 to rank 8 according to the description below. (1) A PMI codebook assumes a precoder structure of W = W₁W₂, wherein W₁is configured by ${W_{1} = \begin{bmatrix}B & 0 \\0 & B\end{bmatrix}},$ and B includes L oversampled 2D DFT beams. In the caseof ranks 1 and 2, the value of L can be set as 1 or 4, and W₂ selects abeam (this is applicable only when L = 4) and indicates QPSK co-phasingwith respect to two polarizations.  (2) The following 1D/2D antenna portlayouts (N₁ and N₂) and over- sampling factors (O₁, O₂) are supported.Number of CSI-RS ports (N₁, N₂) (O₁, O₂) 4 (2, 1) (4, —) 8 (2, 2) (4, 4)(4, 1) (4, —) 12 (3, 2) (4, 4) (6, 1) (4, —) 16 (4, 2) (4, 4) (8, 1) (4,—) 24 (6, 2), (4, 3) (4, 4) (12, 1) (4, —) 32 (8, 2), (4, 4) (4, 4)(16, 1) (4, —)  (3) When L= 4, the beam group (B) pattern, asillustrated in FIG. 23, is supported according to the value of N2.

TABLE 16 The NR supports Type 2 channel state reporting with respect toranks 1 and 2. (1) PMI is used for spatial channel information feedback.(2) In the case of ranks 1 and 2, the PMI codebook assumes the followingprecoder structure.${{{For}\mspace{14mu}{rank}\mspace{14mu} 1\text{:}\mspace{14mu} W}\; = {\begin{bmatrix}{\overset{\sim}{w}}_{0,0} \\{\overset{\sim}{w}}_{1,0}\end{bmatrix} = {W_{1}W_{2}}}},{W\mspace{14mu}{is}\mspace{14mu}{normalized}\mspace{14mu}{to}\mspace{14mu} 1}$${{{For}\mspace{14mu}{rank}\mspace{14mu} 2\text{:}\mspace{14mu} W}\; = {\begin{bmatrix}{\overset{\sim}{w}}_{0,0} & {\overset{\sim}{w}}_{0,1} \\{\overset{\sim}{w}}_{1,0} & {\overset{\sim}{w}}_{1,1}\end{bmatrix} = {W_{1}W_{2}}}},{{columns}\mspace{14mu}{of}\mspace{14mu} W\mspace{14mu}{are}\mspace{14mu}{normalized}\mspace{14mu}{to}\mspace{14mu}\frac{1}{\sqrt{2}}}$${(3)\mspace{14mu}{\overset{\sim}{w}}_{r,l}} = {\sum\limits_{i = 0}^{L - 1}\;{{b_{\;_{k_{1}^{(i)}k_{2}^{(i)}}} \cdot p_{r,l,i}^{({WB})} \cdot p_{r,l,i}^{({SB})} \cdot c_{r,l,i}}\mspace{14mu}\left( {a\mspace{14mu}{weighted}\mspace{14mu}{combination}\mspace{14mu}{of}\mspace{14mu} L\mspace{14mu}{beams}} \right)}}$The value of L may be chosen from among 2, 3, and 4, b_(k) ₁ _(,k) ₂ isan oversampled 2D DFT beam, r is 0 or 1 and refers to polarization, and1 is 0 or 1 and refers to a layer. p_(r,l,i) ^((WB)) is a wideband (WB)beam amplitude scaling factor for beam i, polarization r, and layer 1.p_(r,l,i) ^((SB)) is a subband (SB) beam amplitude scaling factor forbeam i, polarization r, and layer 1. c_(r,l,i) is a beam combinationcoefficient (phase) for beam i, polarization r, and layer 1, which isconfigurable between 2 bits in the case of QPSK and 3 bits in the caseof 8PSK. An amplitude scaling mode is configurable by a combination ofWB and SB(with unequal bit allocation), or by WB only.

TABLE 17 Number of CSI- i1 Payload i1 Payload i2 RS ports (N₁, N₂) (O₁,O₂) (L = 1) (L = 4) payload 4 (2, 1) (4, —) 3 bits 2 bits For rank1, 8(2, 2) (4, 4) 6 bits 4 bits 2 bits for L = 1, (4, 1) (4, —) 4 bits 3bits 4 bits for L = 4 12 (3, 2) (4, 4) 7 bits 5 bits For rank2, (6, 1)(4, —) 4 bits 3 bits Additional 2 bits 16 (4, 2) (4, 4) 7 bits 5 bitsfor i1, (8, 1) (4, —) 5 bits 4 bits 1 bits for L = 1, 24 (6, 2), (4, 4)8 bits 6 bits 3 bits for L = 4 (4, 3) (12, 1) (4, —) 6 bits 5 bits 32(8, 2), (4, 4) 8 bits 6 bits (4, 4) (16, 1) (4, —) 6 bits 5 bits

Table 18 describes a reporting overhead for Type 2 channel statereporting, and particularly describes an example in which, a combinationof amplitudes of a wideband (WB) and a subband (SB), (N₁, N₂)=(4,4), Z=3(8PSK), and K leading coefficients=4, 4, and 6 for L=2, 3, and 4,respectively.

TABLE 18 Strongest SB amp SB phase coefficient WB amp: (1 SB): (1 SB):(1 out of 2L) 3 × 1 × (K −1) (K − 1) + 2 × Total Rotation L-Beam [log₂2L] per (2L − 1) Total WB per (2L − K) payload L [log₂ (O₁-O₂) selectionlayer per layer payload layer per layer (WB + 10 SBs) Rank 1 payload(bits) 2 4 [7 or 8] 2 9 22 3 9 142 3 4 [10 or 12] 3 15 32 3 13 192 4 4[11 or 16] 3 21 29 5 19 279 Rank 2 payload (bits) 2 4 [7 or 8] 4 18 33 618 273 3 4 [10 or 12] 6 30 50 6 26 370 4 4 [11 or 16] 6 42 63 10 38 543

As described above in Table 18, Type I channel state reporting mayreport a channel state to the base station via RI, PMI, CQI, and CSI-RSresource indicator (CRI) based on a codebook, as in the existing LTE. Incontrast, Type II reporting may provide a higher form of resolution viagreater PMI reporting overhead in addition to an implicit CSI similar toType I reporting, and the PMI reporting may be created via a linearcombination of a precoder, a beam, a co-phase, etc. which are used forthe Type I reporting. Also, in order to directly report a channel state,CSI may be reported in an explicit CSI type that is different from anexisting type, and a representative example thereof may be a method ofreporting a covariance matrix of a channel; a type in which implicit andexplicit CSI are combined is also possible. For example, a PMI may beused to report the covariance matrix of the channel, but in addition,the CQI or RI may be reported together.

As mentioned above, Type II requires a high reporting overhead.Therefore, this report may not be suitable for periodic channel statereporting where the number of reportable bits is not high. On the otherhand, when aperiodic channel state reporting is used, since thecorresponding channel state reporting is supported via PUSCH, which iscapable of supporting overheads having a large number of reports, TypeII reporting which requires the overhead having a large number ofreports, may be supported only for aperiodic channel state reporting.

In addition, semi-persistent channel state reporting may support Type 2.In the NR, semi-persistent channel state reporting supports dynamicactivity and inactivity compared to periodic channel state reporting,and thus requires relatively high terminal complexity.

In channel state reporting of the LTE, as noted above in Table 1, thebase station performs, on the basis of a CSI process, a reference signalconfiguration and a report-related configuration for the terminal via ahigher-layer configuration. Accordingly, reporting is made at apreviously configured reporting time point and resources in the case ofperiodic channel state reporting, and configuration informationpreviously configured via a trigger in DCI transferred by the basestation via a downlink control signal is reported in the case ofaperiodic channel state reporting.

In the NR, as noted in FIG. 11, the CSI reporting setting, the resourcesetting, and a link for connecting the same exist in the CSI measurementsetting. When periodic and semi-persistent channel state reporting isused, according to the DCI and RRC setting of the base station or amedia access control (MAC) CE-based activation or deactivation signal, achannel state may be periodically or semi-persistently reported on thebasis of the CSI reporting setting. When aperiodic channel statereporting is used, channel state reporting may be triggered using thefollowing methods.

-   -   Aperiodic channel state report trigger method 1: Triggering        based on a link within a CSI measurement setting; and    -   Aperiodic channel state report trigger method 2: Triggering        based on a CSI reporting setting within a CSI measurement        setting.

Aperiodic channel state report trigger method 1 is a method oftriggering CSI reporting based on a link within a CSI measurementsetting.

FIG. 12 is a diagram of a method for triggering a link within a CSImeasurement setting according to aperiodic channel state report triggermethod 1, according to an embodiment.

In FIG. 12, a base station may configure a link triggered for eachtrigger field to RRC in advance for aperiodic channel state reporting1200. The base station may directly configure a link ID in a triggerconfiguration in order to configure the link to be triggered. The basestation may configure a link triggered using bitmaps indicating links ofall cells configured for the terminal. The instruction order of thebitmaps may be sorted in ascending or descending order based on a cellID and a link ID.

FIG. 13 is a diagram of an indication order of bitmaps, according to anembodiment. An indication order of a bitmap 1300 may first be arrangedbased on cell IDs, and may be arranged in ascending order from MSB toLSB based on the link IDs within the same cell IDs. In FIG. 13, the cellIDs are preferentially arranged; however, the link IDs may be arrangedfirst, or may be sorted in descending order.

Aperiodic channel state report trigger method 2 is a method fortriggering CSI reporting based on a CSI reporting setting within a CSImeasurement setting.

FIG. 14 is a diagram of a method for triggering a CSI reporting settingwithin a trigger measurement setting according to aperiodic channelstate report trigger method 2, according to an embodiment. In FIG. 14, abase station may configure, in advance, a CSI reporting settingtriggered for each trigger field via RRC for aperiodic channel statereporting 1400. The base station may directly configure a CSI reportingsetting ID in a trigger configuration in order to configure thetriggered CSI reporting setting. The base station may configure atriggered CSI reporting setting by using bitmaps indicating CSIreporting settings of all cells configured for the terminal. Theinstruction order of the bitmaps may be arranged in ascending ordescending order based on a cell ID, a CSI reporting setting ID, etc.

FIG. 15 is a diagram of an indication order of bitmaps, according to anembodiment.

As shown in FIG. 15, an indication order of a bitmap 1500 may first bearranged based on the cell IDs, and may be arranged in ascending orderfrom MSB to LSB based on channel state report IDs within the same cellIDs. In FIG. 15, the cell IDs are preferentially arranged; however, thechannel state report IDs may be arranged first, or may be sorted indescending order.

In order for a base station to trigger CSI reporting based on the links,the base station may cause a terminal to perform aperiodic channel statereporting to the base station, via DCI by using the trigger fields shownin Tables 19, 20, and 21.

TABLE 19 Value of CSI request field Description ‘000’ No aperiodic CSIreport is triggered ‘001’ Aperiodic CSI report is triggered for a set oflink(s) configured by higher layers for serving cell ‘010’ Aperiodic CSIreport is triggered for a 1^(st) set of link(s) configured by higherlayers . . . . . .

TABLE 20 Value of CSI request field Description ‘000’ Aperiodic CSIreport is triggered for a set of link(s) configured by higher layers forserving cell ‘001’ Aperiodic CSI report is triggered for a 1^(st) set oflink(s) configured by higher layers ‘010’ Aperiodic CSI report istriggered for a 2^(nd) set of link(s) configured by higher layers . . .. . .

TABLE 21 Value of CSI request field Description ‘000’ Aperiodic CSIreport is triggered for a 1^(st) set of link(s) configured by higherlayers ‘001’ Aperiodic CSI report is triggered for a 2^(nd) set oflink(s) configured by higher layers ‘010’ Aperiodic CSI report istriggered for a 3^(rd) set of link(s) configured by higher layers . . .. . .

In Table 19, the base station may perform triggering for the terminal byusing the indication fields, so that aperiodic channel state reportingis not triggered or so that all links of a corresponding cell may betriggered, and from the bit “010” subsequent to “001”, links triggeredfor channel state reporting via a pre-RRC setting may be triggered asdescribed above with respect to the trigger method 1. The trigger fieldsused in Table 20 exclude a case involving no triggering therefrom. Inthis case, there may be an option involving no triggering of channelstate reporting, in pre-configuration of a trigger field for which “001”or the like can be configured. According to Table 21, flexibility may beprovided in configuration of the base station, by increasing the degreeof freedom except for aperiodic CSI reporting setting that correspondsto reporting all links of one cell in use. As noted above in Table 20,there may also be an option involving no triggering of channel statereporting, in pre-configuration of a trigger field for which “000” orthe like can be configured.

As described above, in order to trigger channel state reporting based onthe CSI reporting setting, the base station may cause the terminal toperform aperiodic channel state reporting to the base station, via DCIby using the trigger fields shown in TABLEs 22, 23, and 24.

TABLE 22 Value of CSI request field Description ‘000’ No aperiodic CSIreport is triggered ‘001’ Aperiodic CSI report is triggered for a set ofCSI reporting setting(s) configured by higher layers for serving cell‘010’ Aperiodic CSI report is triggered for a 1^(st) set of CSIreporting setting(s) configured by higher layers . . . . . .

TABLE 23 Value of CSI request field Description ‘000’ Aperiodic CSIreport is triggered for a set of CSI reporting setting(s) configured byhigher layers for serving cell ‘001’ Aperiodic CSI report is triggeredfor a 1^(st) set of CSI reporting setting(s) configured by higher layers‘010’ Aperiodic CSI report is triggered for a 2^(nd) set of CSIreporting setting(s) configured by higher layers . . . . . .

TABLE 24 Value of CSI request field Description ‘000’ Aperiodic CSIreport is triggered for a 1^(st) set of CSI reporting setting(s)configured by higher layers ‘001’ Aperiodic CSI report is triggered fora 2^(nd) set of CSI reporting setting(s) configured by higher layers‘010’ Aperiodic CSI report is triggered for a 3^(rd) set of CSIreporting setting(s) configured by higher layers . . . . . .

In Table 22, the base station may perform triggering for the terminal byusing the indication fields, so that aperiodic channel state reportingmay not be triggered or so that all CSI reporting settings of acorresponding cell may be triggered, and from the bit “010” subsequentto “001”, CSI reporting settings triggered for channel state reportingvia a pre-RRC setting may be triggered as described above with respectto the trigger method 2. The trigger fields used in Table 23 exclude thecase where no channel state reporting is triggered.

In this case, there may be an option involving no triggering of channelstate reporting in the pre-configuration of a trigger field for which“001” or the like can be configured. According to Table 24, flexibilitymay be provided in configuration of the base station, by increasing thedegree of freedom except for aperiodic CSI reporting setting, whichcorresponds to reporting all CSI reporting settings of one cell in use.As noted above in Table 23, there may also be an option involving notriggering of channel state reporting in the pre-configuration of atrigger field for which “000” or the like can be configured.

The indication fields may be used to indirectly indicate an aperiodicCSI-RS for channel measurement and interference measurement.

FIG. 16 is a diagram of indirect indication of an aperiodic CSI-RS byusing an aperiodic channel state report indication field, according toan embodiment.

In FIG. 16, a base station triggers channel state reporting by using alink. When a resource supported for channel measurement in a resourcesetting connected to a corresponding link corresponds to a periodicCSI-RS 1600, corresponding aperiodic channel state reporting may beperformed based on a channel measured at an existing periodic CSI-RSresource. When the resource supported for channel measurement in theresource setting connected to the corresponding link corresponds to anaperiodic CSI-RS 1610, corresponding aperiodic channel state reportingmay be performed based on a channel measured at an aperiodicallyconfigured CSI-RS resource. An aperiodic channel state report triggerand an aperiodic CSI-RS may always be transmitted in the same slot orsubframe. As mentioned above, it is also possible that channel statereporting and aperiodic CSI-RS are triggered through a CSI reportingsetting rather than a link.

In order to support the channel state reporting, resources for a desiredsignal and interference measurement may be configured for the terminalvia the resource setting illustrated in FIG. 11. The following RRCparameters may be considered for resource setting, as shown in Table 25.

TABLE 25 Parameter name Description Value range CSI-RS-ResourceConfigCSI-RS resource configuration CSI-RS-ResourceConfigId CSI-RS resourceconfiguration ID 0 . . . CSI-RS- ResourceMax − 1 ResourceConfigType Timedomain behavior of resource configuration aperiodic, semi-persistent, orperiodic CSI-RS-timeConfig Contains periodicity and slot offset forperiodic/semi- persistent CSI-RS NrofPorts Number of ports 1, 2, 4, 8,12, 16, [24], 32 CSI-RS-ResourceMapping Include parameters to captureOFDM symbol and subcarrier occupancy of the CSI-RS resource within aslot CDMType Includes parameters to capture CDM value (1, 2, 4, or 8),CDM pattern (freq only, time and freq, time only) CSI-RS-Density Densityof CSI-RS resource measured in RE/port/PRB e.g., ½, 1, >1CSI-RS-FreqBand Includes parameters to enable configuration of widebandand partial band CSI-RS Pc Power offset of NZP CSI-RS RE to PDSCH REScramblingID Scrambling ID

Based on the resource setting, beam measurement, reporting, andmanagement may be supported in the NR. A large number of antennas, suchas 1024 antennas, and a high frequency band, such as 30 GHz, aresupported in NR MIMO. Wireless communication using a millimeter waveexhibits high linearity and high path loss due to the characteristics ofa corresponding band. In order to overcome this problem, hybridbeamforming, in which RF and antenna-based analog beamforming anddigital-precoding-based digital beamforming can be combined, isrequired.

FIG. 17 is a diagram of a hybrid beamforming system 1700, according toan embodiment.

In FIG. 17, a base station and a terminal include an RF chain and aphase shifter for digital beamforming and analog beamforming. An analogbeamforming scheme on a transmission side corresponds to a method ofchanging the phase of a signal transmitted from each antenna, via thephase shifter, thereby concentrating the corresponding signal in aspecific direction, wherein the signal is transmitted from each antennaby using a plurality of antennas. To this end, an array antenna, inwhich a plurality of antenna elements are aggregated, can be used. Whentransmission beamforming is used, it is possible to increase the arrivaldistance of signal waves, and since signals are hardly transmitted indirections other than a corresponding direction, interference on otherusers can be considerably reduced. Similarly, a reception side mayperform reception beamforming by using a reception array antenna, inwhich the sensitivity of reception signals entering in a correspondingdirection is increased by concentrating the reception of radio waves ina specific direction, and excluding a signal entering in directionsother than the corresponding direction from the reception signals,thereby blocking an interference signal.

Conversely, as a transmission frequency increases, the wavelength of aradio wave becomes shorter. For example, when antennas are formed athalf-wave intervals, an array antenna may include more element antennaswithin an area of the same size. Therefore, a communication systemoperating at a high frequency band is well positioned to apply thebeamforming technique because the communication system may acquire arelatively higher antenna gain in comparison with using the beamformingtechnique at a low frequency band.

In this beamforming technique, in order to obtain a higher antenna gain,hybrid beamforming is used, in which the hybrid beamforming combinesdigital precoding used to achieve a high data transmission rate effectin an existing multi-antenna system with the analog beamformingtechnique. When a beam is formed via analog beamforming, and one or moreanalog beams are formed, a signal is transmitted by employing digitalprecoding similar to that applied in existing multiple antennas in abaseband, so that a more reliable signal may be received or a highersystem capacity may be expected. The disclosure proposes a method for,when a base station and a terminal support analog, digital, or hybridbeamforming, measuring the quality of a beam according to the beamswitching capability of the base station and the terminal, and reportingand using corresponding information.

With respect to beamforming, it is important to select a directionoptimized for the corresponding base station and terminal. In order toselect an optimized beam direction, the base station and the terminalmay support beam-sweeping by using a plurality of time and frequencyresources.

FIG. 18 is a diagram of a beam-sweeping operation of a terminal and abase station in time resources, according to an embodiment.

In FIG. 18, a terminal or a base station transmits a reference signal byusing a different beam for a time resource in order to select a beam forthe terminal or the base station. A base station or a terminal havingreceived the reference signal may measure the quality of thecorresponding reference signal based on a CSI of the reference signal,reference signal received power (RSRP), a reference signal receivedquality (RSRQ), etc., and may select one or multiple transmission orreception beams according to the corresponding result. In FIG. 17, areference signal is transmitted based on a different beam via adifferent time resource. However, the same transmission scheme may beapplied to frequency, cyclic shift, a code resource, etc. As shown inFIG. 18, a plurality of transmission beams 1800 may be transmitted fortransmission beam-sweeping, and it is also possible to repeatedly applyone transmission beam and perform transmission 1810 for receptionbeam-sweeping.

A beam management operation, such as beam-sweeping, may also beperformed based on periodic, semi-persistent, or aperiodic CSI-RStransmission and channel state reporting/beam reporting, and the channelstate report framework (resource setting, CSI reporting setting, CSImeasurement setting, links, etc.) depicted in FIGS. 11 to 16.

In supporting the channel state reporting or the beam reporting, forresource setting in the NR, a plurality of CSI-RS resources areconfigured into a CSI-RS resource set in order to transmit a pluralityof beams for transmission beam-sweeping and to repeatedly transmit asingle transmission beam for reception beam-sweeping, and whether eachof the CSI-RS resources corresponds to an individual CSI-RS resource oran identical CSI-RS resource is repeated may be configured, and forthis, the RRC setting parameters in Table 26 described below may beprovided.

TABLE 26 Parameter name Description Value range ResourceSetConfigListContains up to ResourceSetMax resource set configurations(ResourceSetConfig) ResourceSetConfig Resource set configurationResourceSetConfigId Resource set 0 . . . configuration ID ResourceSetMax− 1 CSI-RS- Contains up to CSI-RS- ResourceConfigList ResourcePerSetMaxCSI-RS resource configurations (CSI-RS- ResourceConfig) CSI-RSConfiguration ResourceRepetitionConfig of CSI-RS resource repetitionON/OFF

In Table 26, ResourceSetConfigList enables the configuration of aplurality of CSI-RS resource sets. A plurality of CSI-RS resource setsmay be configured, and individual CSI-RS resource sets are individuallyconfigured via ResourceSetConfig. ResourceSetConfig hasResourceSetConfigld, CSI-RS-ResourceConfigList, and CSI-RSResourceRepetitionConfig configurations. ResourceSetConfigld may allowthe configuration of an ID for a CSI-RS resource set configuration, andCSI-RS-ResourceConfigList may allow the configuration of IDs of CSI-RSresources configured into a corresponding CSI-RS resource set, based onthe IDs of CSI-RS resources described in Table 25, so as to indicate theCSI-RS resource configured into the CSI-RS resource set. For CSI-RSresources configured into a corresponding CSI-RS resource set, CSI-RSResourceRepetitionConfig may allow configuration of whether individualCSI-RS resources are transmitted based on a different beam fortransmission beam-sweeping or individual CSI-RS resources supportrepetition of the same CSI-RS resource. In order to indicate whether thecorresponding CSI-RS resource set supports the same beam, CSI-RSResourceRepetitionConfig may be expressed as BeamRepetitionConfig, orthe like.

In the configuration of CSI-RS resource repetition in the correspondingCSI-RS resource set configuration, only a 1-port CSI-RS resource or a 1-or 2-port CSI-RS resource may be configured as each CSI-RS resource. Inthe transmission beam-sweeping and the reception beam-sweeping mentionedin FIG. 18, the number of corresponding transmission beams may be large,such as 1024 transmission beams, and the number may become larger whenconsidering the reception beam-sweeping. Therefore, the number ofcorresponding antenna ports may be limited to 1 port or 2 ports in orderto configure CSI-RS resources necessary for corresponding sweeping, sothat the overhead necessary for reference signal transmission may bereduced and efficient beam management may be performed.

In addition, when the CSI-RS resource repetition is configured withinthe CSI-RS resource set, when OFDM symbols at which corresponding CSI-RSresources are transmitted are the same according toCSI-RS-ResourceMapping configuration of each of the CSI-RS resources,the CSI-RS resources may not be allowed for repetition configuration orthe terminal may be configured to disregard the correspondingconfiguration; this is because it is difficult for the terminal to usethe CSI-RS in the same OFDM symbol to measure the quality of a differentreception beam, in sweeping a plurality of reception beams of theterminal.

In addition, when the CSI-RS resource is repeated, configurations otherthan CSI-RS-ResourceMapping configuration, which are ResourceConfigType,CSI-RS-timeConfig, NrofPorts, CDMType, CSI-RS-Density, CSI-RS-FreqBand,Pc, and ScramblingID configurations, may not be allowed for a differentconfiguration specific to a CSI-RS resource, or the terminal may beconfigured to disregard the corresponding configuration. The reason forthis is that, when the terminal sweeps a plurality of reception beams ofthe terminal, when the densities of the CSI-RSs are different, arelative comparison of CQIs or RSRP for corresponding beam measurementsmay be difficult. When transmission occurs frequently at one CSI-RSresource while transmission occurs relatively infrequently at adifferent CSI-RS resource due to a difference in each configured CSI-RSresource period, it is difficult for the reception beam-sweepingrequired by the terminal to be completely performed. In addition, whenboosting of corresponding CSI-RS power Pc or the CSI-RS-FreqBand that isa transmission frequency band are configured differently for the samebeam transmission, RSRP specific to a reception beam may vary, and theaccuracy may be lowered even if the terminal corrects the RSRP.

Therefore, at CSI-RS resource repetition for corresponding receptionbeam-sweeping, in order to reduce the hardware implementation complexityof the terminal in the CSI-RS repetition configuration and toefficiently perform a terminal reception beam-sweeping operation,configuration of the CSI-RS resource included in the correspondingCSI-RS resource set may be limited. The method for limiting theconfiguration of the CSI-RS resource included in the resource set whenCSI-RS resource repetition is configured may be as follows.

-   -   Resource setting restriction method 1: Reusing specific CSI-RS        resource setting other than CSI-RS-ResourceMapping.    -   Resource setting restriction method 2: Repeatedly performing        recognition when a plurality of identical CSI-RS resource IDs        are configured.    -   A relative symbol offset required for CSI-RS-ResourceMapping may        be additionally configured.    -   Resource setting restriction method 3: When repetition is        configured, when the CSI-RS setting is not the same,        disregarding the corresponding CSI-RS setting.

Resource setting restriction method 1 is a method of reusing theconfiguration of a first CSI-RS resource except for a variableparameter, such as CSI-RS-ResourceMapping. When corresponding repetitionis configured, configuration of a specific CSI-RS resource, except forsome parameters required to be configured differently for each resource,may be reused. The specific CSI-RS resource may be predefined as aspecific resource (e.g., the first CSI-RS resource, etc.) in thestandard, or a CSI-RS resource having a configuration used forrepetition may be additionally indicated via RRC or MAC CE.

Resource setting restriction method 2 is a method for, when a pluralityof identical CSI-RS resource IDs are configured, causing theconfiguration to be recognized as repetition. In order to use the sameparameter, the same CSI-RS resource may be configured so as to providenotification of repetition of the same resource. Since the terminal maybe able to identify via a corresponding ID whether repetition isperformed, CSI-RS resource repetition transmission may be identified viathe same CSI-RS resource ID configured to the CSI-RS resource setwithout an additional configuration (CSI-RS ResourceRepetitionConfig)field. In this case, the CSI-RS resource repetition transmission may beapplied to all or part of the resource set. Also, since the CSI-RSresource used for repetition should not be transmitted at the same OFDMsymbol as mentioned above, CSI-RS-ResourceMapping may be allowed forexceptional use, or a relative symbol offset required for repetition maybe additionally configured.

Resource setting restriction method 3 is a method for, when repetitionhas been configured, disallowing or disregarding a corresponding CSI-RSsetting when the CSI-RS setting is not the same. Since the sameparameter should be used when repetition is configured, when repetitionhas been configured to a CSI-RS resource that does not use the sameparameters in parameters other than some parameters allowing a differentconfiguration, the terminal may determine that the correspondingconfiguration is wrong and may disregard the corresponding CSI-RSsetting.

In the disclosure, descriptions have been made for an example in which abase station supports a transmission beam, while a terminal supports areception beam. However, it is also possible that a base stationsupports a reception beam while a terminal supports a transmission beam,or that all of multiple terminals support both transmission andreception beams. Further, in the disclosure, descriptions have been madebased on a CSI-RS, but embodiments of the disclosure may also beapplicable to a sounding reference signal (SRS).

FIG. 19 is a flowchart of a method of a terminal according to anembodiment. Referring to FIG. 9, in step 1910, a terminal receivesmeasurement-setting and resource-setting information. The informationmay include information on a reference signal for channel measurement.For example, a reference signal type, a number of ports of the referencesignal, a codebook type, N₁ and N₂, i.e., the number of antennas foreach dimension, O₁ and O₂, i.e., an oversampling factor for eachdimension, one subframe config for transmission of a plurality ofCSI-RSs and a plurality of resource configs for position configuration,codebook subset restriction-related information, CSI reporting-relatedinformation, a CSI-process index, a candidate number for timingindication between an aperiodic channel state report trigger andaperiodic channel state reporting, and/or transmission power information(Pc) may be included, and a terminal may identify at least one thereof.

In step 1920, the terminal may configure a piece of feedbackconfiguration information via the CSI reporting setting used in acorresponding measurement setting. The information may includeinformation on whether to report PMI/CQI, a period and offset, an RIperiod and offset, a CRI period and offset, a status ofwideband/subband, a submode, a candidate number for timing indicationbetween an aperiodic channel state report trigger and aperiodic channelstate reporting, etc.

In step 1930, when a reference signal is received based on thecorresponding information, the terminal estimates a channel between anantenna of a base station and a reception antenna of the terminal on thebasis of the received reference signal.

In step 1940, based on the estimated channel, the terminal may generatefeedback information, such as rank, PMI, and CQI, by using a receivedfeedback configuration, and may select an optimum CRI on the basisthereof. Subsequently, in step 1950, the terminal transmits, to the basestation, the feedback information at a feedback timing determinedaccording to the feedback configuration of the base station or theaperiodic channel state report trigger, and the timing indicationbetween the aperiodic channel state report trigger and the aperiodicchannel state reporting, and completes a procedure of generating andreporting channel feedback.

FIG. 20 is a flowchart of a method of a base station according to anembodiment.

Referring to FIG. 20, in step 2010, a base station transmits, to aterminal, a reference signal for channel measurement and configurationinformation for a CSI reporting setting. The configuration informationmay include a type of each reference signal, a time and frequencyresource position, a service type, a support feedback type, and ameasurement subset. The configuration information may include a numberof ports for a reference signal for transmission of the referencesignal, N₁ and N₂, i.e., the number of antennas for each dimension, O₁and O₂, i.e., an oversampling factor for each dimension, one subframeconfig for transmission of a plurality of reference signals and aplurality of resource configs for position configuration, codebooksubset restriction-related information, CSI reporting-relatedinformation, a CSI-process index, and/or Pc.

Subsequently, in step 2020, the base station transmits, to the terminal,feedback configuration information based on at least one CSI-RS. Thecorresponding information may include a PMI/CQI period and offset, an RIperiod and offset, a CRI period and offset, a status ofwideband/subband, a submode, a candidate number for timing indicationbetween an aperiodic channel state report trigger and aperiodic channelstate reporting, etc. Subsequently, the base station transmits aconfigured CSI-RS to the terminal. The terminal estimates a channel foreach antenna port, and estimates an additional channel with respect tovirtual resources on the basis of the estimated channel. The terminalmay determine feedback, generates a CRI, a PMI, an RI, and a CQIcorresponding thereto, and transmit the same to the base station. Instep 2030, the base station receives feedback information from theterminal at a determined timing and uses the same to determine thechannel state between the terminal and the base station.

FIG. 21 is a diagram of a terminal, according to an embodiment.

Referring to FIG. 21, a terminal includes a transceiver 2110 and acontroller 2120. The transceiver 2110 may transmit data to or receivedata from the outside (e.g., a base station). The transceiver 2110 maytransmit, to a base station, feedback information under the control ofthe controller 2120. The controller 2120 controls statuses andoperations of all elements forming the terminal. Specifically, thecontroller 2120 generates feedback information based on the informationassigned from the base station. Also, the controller 2120 controls thetransceiver 2110 to transmit, to the base station, generated channelinformation according to timing information assigned from the basestation. The controller 2120 may include a channel estimation unit 2130.The channel estimation unit 2130 determines the position of acorresponding resource in time and frequency resources via service andfeedback information received from the base station, and identifiesnecessary feedback information via CSI-RS and feedback allocationinformation related thereto. A channel is estimated using the receivedCSI-RS based on the feedback information.

Although FIG. 21 has described an example in which the terminal isformed of the transceiver 2110 and the controller 2120, the disclosuremay not be limited thereto, and may further include various elementsbased on a function executed in the terminal. For example, the terminalmay include a display that displays the present status of the terminal,an input unit through which a signal for executing a function is inputfrom a user, a storage unit that stores data generated in the terminal,or the like. Also, while it is illustrated that the channel estimationunit 2130 is included in the controller 2120, the channel estimationunit 2130 can be a component separate from the controller 2120. Thecontroller 2120 may control the transceiver 2110 to receiveconfiguration information associated with a reference signal resource,from the base station. The controller 2120 may measure the referencesignal, and may control the transceiver 2110 to receive, from the basestation, feedback configuration information for generating feedbackinformation on the basis of a result of the measurement.

The controller 2120 may measure one or more reference signals receivedthrough the transceiver 2110, and may generate feedback informationbased on the feedback configuration information. The controller 2120 maycontrol the transceiver 2110 to transmit, to the base station, thegenerated feedback information at a feedback timing based on thefeedback configuration information. The controller 2120 may receive aCSI-RS from the base station, may generate feedback information based onthe received CSI-RS, and may transmit the generated feedback informationto the base station.

The controller 2120 may receive a CSI-RS from the base station, maygenerate feedback information on the basis of the received CSI-RS, andmay transmit the generated feedback information to the base station. Thecontroller 2120 may select one precoding matrix with respect to allantenna port groups of the base station. The controller 2120 may receivefeedback configuration information from the base station, may receive aCSI-RS from the base station, may generate feedback information based onthe received feedback configuration information and the received CSI-RS,and may transmit the generated feedback information to the base station.

FIG. 22 is a diagram of a base station, according to an embodiment.Referring to FIG. 22, the base station includes a controller 2210 and atransceiver 2220. The controller 2210 controls statuses and operationsof all elements forming the base station. The controller 2210 assigns arelated configuration for a terminal to acquire resource information,allocates a CSI-RS resource for channel estimation to the terminal, andallocates a feedback resource and a feedback timing to the terminal. Tothis end, the controller 2210 may further include a resource allocationunit 2230. The controller 2210 may allocate a feedback configuration anda feedback timing to prevent collisions between feedback from multipleterminals, may receive configured feedback information at thecorresponding timing, and may interpret the same. The transceiver 2220may execute transmission and reception of data, a reference signal, andfeedback information with the terminal. The transceiver 2220 maytransmit a CSI-RS to the terminal, and may receive feedback associatedwith channel information from the terminal, through resources allocatedunder the control of the controller 2210. A reference signal istransmitted based on a CRI, a rank, a part of PMI information, a CQI,etc., which are obtained from channel state information transmitted bythe terminal.

While it is illustrated that the resource allocation unit 2230 isincluded in the controller 2210, the resource allocation unit 2230 maybe a component separate from the controller 2210. The controller 2210may control the transceiver 2230 to transmit, to the terminal,configuration information associated with a reference signal, or maygenerate the reference signal. The controller 2210 may control thetransceiver 2220 to transmit, to the terminal, feedback configurationinformation for generation of feedback information according to theresult of the measurement. The controller 2210 may transmit the at leastone reference signal to the terminal, and may control the transceiver2220 to receive the feedback information transmitted from the terminalat a feedback timing according to the feedback configurationinformation. The controller 2210 may transmit the feedback configurationinformation to the terminal, may transmit a CSI-RS to the terminal, andmay receive the feedback information generated based on the feedbackconfiguration information and the CSI-RS from the terminal. Thecontroller 2210 may transmit feedback configuration informationcorresponding to each antenna port group of the base station, as well asadditional feedback configuration information based on a relationshipbetween antenna port groups. The controller 2210 may transmit a CSI-RSbeam formed based on the feedback information to the terminal, and mayreceive the feedback information generated based on the CSI-RS from theterminal.

While the disclosure has been shown and described with reference tocertain embodiments thereof, it will be understood by those skilled inthe art that various changes in form and details may be made thereinwithout departing from the scope of the disclosure. Therefore, the scopeof the disclosure should not be defined as being limited to theembodiments, but should be defined by the appended claims andequivalents thereof

What is claimed is:
 1. A method performed by a base station in acommunication system, the method comprising: transmitting, to aterminal, configuration information on a channel state informationreference signal (CSI-RS) resource set, the configuration informationincluding configurations on a plurality of CSI-RS resources included inthe CSI-RS resource set and information on a CSI-RS repetition, whereinthe information on the CSI-RS repetition is set as either on or off, andwherein the plurality of CSI-RS resources included in the CSI-RSresource set are associated with a same beam in case that theinformation on the CSI-RS repetition is set as on; in case that theinformation on the CSI-RS repetition is set as on, transmitting, to theterminal, a plurality of CSI-RSs corresponding to the plurality ofCSI-RS resources based on the same beam; and receiving, from theterminal, feedback information, wherein the feedback informationincludes an indicator of a selected CSI-RS resource and a power relatedto the selected CSI-RS resource in case that the information on theCSI-RS repetition is set as off.
 2. The method of claim 1, wherein incase that the information on the CSI-RS repetition is set as on, thefeedback information includes a power related to a CSI-RS resource. 3.The method of claim 1, wherein in case that the information on theCSI-RS repetition is set as on, a periodicity is the same for all of theplurality of CSI-RS resources.
 4. The method of claim 1, wherein in casethat the information on the CSI-RS repetition is set as on, a number ofantenna ports is set to 1 or 2 for all of the plurality of CSI-RSresources.
 5. The method of claim 1, further comprising: transmitting,to the terminal, the plurality of CSI-RSs corresponding to the pluralityof CSI-RS resources based on different beams, in case that theinformation on the CSI-RS repetition is set as off.
 6. A methodperformed by a terminal in a communication system, the methodcomprising: receiving, from a base station, configuration information ona channel state information reference signal (CSI-RS) resource set, theconfiguration information including configurations on a plurality ofCSI-RS resources included in the CSI-RS resource set and information ona CSI-RS repetition, wherein the information on the CSI-RS repetition isset as either on or off, and wherein the plurality of CSI-RS resourcesincluded in the CSI-RS resource set are associated with a same beam incase that the information on the CSI-RS repetition is set as on;receiving, from the base station, a plurality of CSI-RSs correspondingto the plurality of CSI-RS resources based on the configurationinformation, wherein the plurality of CSI-RSs are transmitted based onthe same beam in case that the information on the CSI-RS repetition isset as on; obtaining feedback information based on the receivedplurality of CSI-RSs; and transmitting, to the base station, thefeedback information, wherein the feedback information includes anindicator of a selected CSI-RS resource and a power related to theselected CSI-RS resource in case that the information on the CSI-RSrepetition is set as off.
 7. The method of claim 6, wherein, in casethat the information on the CSI-RS repetition is set as on, the feedbackinformation includes a power related to a CSI-RS resource.
 8. The methodof claim 6, wherein in case that the information on the CSI-RSrepetition is set as on, a periodicity is the same for all of theplurality of CSI-RS resources.
 9. The method of claim 6, wherein in casethat the information on the CSI-RS repetition is set as on, a number ofantenna ports is set to 1 or 2 for all of the plurality of CSI-RSresources.
 10. The method of claim 6, wherein the terminal does notassume that the plurality of CSI-RSs are transmitted on the same beam incase that the information on the CSI-RS repetition is set as off.
 11. Abase station in a communication system, the base station comprising: atransceiver; and a controller operably coupled to the transceiver andconfigured to: transmit, to a terminal, configuration information on achannel state information reference signal (CSI-RS) resource set, theconfiguration information including configurations on a plurality ofCSI-RS resources included in the CSI-RS resource set and information ona CSI-RS repetition, wherein the information on the CSI-RS repetition isset as either on or off, and wherein the plurality of CSI-RS resourcesincluded in the CSI-RS resource set are associated with a same beam incase that the information on the CSI-RS repetition is set as on, in casethat the information on the CSI-RS repetition is set as on, transmit, tothe terminal, a plurality of CSI-RSs corresponding to the plurality ofCSI-RS resources based on the same beam, and receive, from the terminal,feedback information, wherein the feedback information includes anindicator of a selected CSI-RS resource and a power related to theselected CSI-RS resource in case that the information on the CSI-RSrepetition is set as off.
 12. The base station of claim 11, wherein incase that the information on the CSI-RS repetition is set as on, thefeedback information includes a power related to a CSI-RS resource. 13.The base station of claim 11, wherein in case that the information onthe CSI-RS repetition is set as on, a periodicity is the same for all ofthe plurality of CSI-RS resources.
 14. The base station of claim 11,wherein in case that the information on the CSI-RS repetition is set ason, a number of antenna ports is set to 1 or 2 for all of the pluralityof CSI-RS resources.
 15. The base station of claim 11, wherein thecontroller is further configured to: transmit, to the terminal, theplurality of CSI-RSs corresponding to the plurality of CSI-RS resourcesbased on different beams, in case that the information on the CSI-RSrepetition is set as off.
 16. A terminal in a communication system, theterminal comprising: a transceiver; and a controller operably coupled tothe transceiver and configured to: receive, from a base station,configuration information on a channel state information referencesignal (CSI-RS) resource set, the configuration information includingconfigurations on a plurality of CSI-RS resources included in the CSI-RSresource set and information on a CSI-RS repetition, wherein theinformation on the CSI-RS repetition is set as either on or off, andwherein the plurality of CSI-RS resources included in the CSI-RSresource set are associated with a same beam in case that theinformation on the CSI-RS repetition is set as on, receive, from thebase station, a plurality of CSI-RSs corresponding to the plurality ofCSI-RS resources based on the configuration information, wherein theplurality of CSI-RSs are transmitted based on the same beam in case thatthe information on the CSI-RS repetition is set as on, obtain feedbackinformation based on the received plurality of CSI-RSs, and transmit, tothe base station, the feedback information, wherein the feedbackinformation includes an indicator of a selected CSI-RS resource and apower related to the selected CSI-RS resource in case that theinformation on the CSI-RS repetition is set as off.
 17. The terminal ofclaim 16, wherein, in case that the information on the CSI-RS repetitionis set as on, the feedback information includes a power related to aCSI-RS resource.
 18. The terminal of claim 16, wherein in case that theinformation on the CSI-RS repetition is set as on, a periodicity is thesame for all of the plurality of CSI-RS resources.
 19. The terminal ofclaim 16, wherein in case that the information on the CSI-RS repetitionis set as on, a number of antenna ports is set to 1 or 2 for all of theplurality of CSI-RS resources.
 20. The terminal of claim 16, wherein thecontroller is further configured to: not assume that the plurality ofCSI-RSs are transmitted based on the same beam in case that theinformation on the CSI-RS repetition is set as off.